diff --git a/README.md b/README.md
index 1ee97b8..f2bce41 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,21 @@ api = Kintone::Api.new("example.cybozu.com", "Administrator", "cybozu")
 
 # Use token authentication
 api = Kintone::Api.new("example.cybozu.com", "authtoken")
+
+# Use OAuth authentication
+api = Kintone::OAuthApi.new("example.cybozu.com", "access_token")
+# if set oauth options below, you can refresh the access_token.
+oauth_options = {
+  client_id: 'client_id',
+  client_secret: 'client_secret',
+  refresh_token: 'refresh_token',
+  expires_at: 1599921045
+}
+api = Kintone::OAuthApi.new("example.cybozu.com", "access_token", oauth_options)
+# get new token.
+api.refresh!
+api.access_token.token
+# => "new_access_token"
 ```
 
 ### Supported API
diff --git a/kintone.gemspec b/kintone.gemspec
index a862a66..bb44ba4 100644
--- a/kintone.gemspec
+++ b/kintone.gemspec
@@ -18,6 +18,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ['lib']
 
+  spec.add_runtime_dependency 'oauth2', '>=1.4.4'
   spec.add_runtime_dependency 'faraday', '>=0.9.2'
   spec.add_runtime_dependency 'faraday_middleware', '>=0.10.0'
 
diff --git a/lib/kintone.rb b/lib/kintone.rb
index 8c0f3fa..b1db285 100644
--- a/lib/kintone.rb
+++ b/lib/kintone.rb
@@ -1,5 +1,6 @@
 require 'kintone/version'
 require 'kintone/api'
+require 'kintone/oauth_api'
 require 'kintone/type'
 
 module Kintone
diff --git a/lib/kintone/oauth_api.rb b/lib/kintone/oauth_api.rb
new file mode 100644
index 0000000..ec560b2
--- /dev/null
+++ b/lib/kintone/oauth_api.rb
@@ -0,0 +1,102 @@
+require 'oauth2'
+
+class Kintone::OAuthApi < Kintone::Api
+  # @return [OAuth2::AccessToken]
+  attr_reader :access_token
+
+  # @param [String] domain the kintone's domain (e.g. 'foobar.cybozu.com').
+  # @param [String] token the Access Token value.
+  # @param [Hash] opts the options to create the Access Token with.
+  # @option opts [String] :client_id (nil) the client_id value.
+  # @option opts [String] :client_secret (nil) the client_secret value.
+  # @option opts [String] :refresh_token (nil) the refresh_token value.
+  # @option opts [FixNum, String] :expires_at (nil) the epoch time in seconds in which AccessToken will expire.
+  # @yield [builder] The Faraday connection builder
+  def initialize(domain, token, opts = {}, &block)
+    client_options = {
+      site: "https://#{domain}",
+      token_url: '/oauth2/token',
+      authorize_url: '/oauth2/authorization',
+      connection_build: connection_builder(&block)
+    }
+    client = ::OAuth2::Client.new(opts[:client_id], opts[:client_secret], client_options)
+    @access_token = ::OAuth2::AccessToken.new(client, token, refresh_token: opts[:refresh_token], expires_at: opts[:expires_at])
+  end
+
+  def refresh!
+    @access_token = @access_token.refresh!
+  end
+
+  def get(url, params = {})
+    opts = request_options(params: params, headers: nil)
+    request(:get, url, opts)
+  end
+
+  def post(url, body)
+    json_body = body.to_json if body.respond_to?(:to_json)
+    opts = request_options(body: json_body)
+    request(:post, url, opts)
+  end
+
+  def put(url, body)
+    json_body = body.to_json if body.respond_to?(:to_json)
+    opts = request_options(body: json_body)
+    request(:put, url, opts)
+  end
+
+  def delete(url, body = nil)
+    json_body = body.to_json if body.respond_to?(:to_json)
+    opts = request_options(body: json_body)
+    request(:delete, url, opts)
+  end
+
+  def post_file(url, path, content_type, original_filename)
+    body = { file: Faraday::UploadIO.new(path, content_type, original_filename) }
+    headers = { 'Content-Type' => 'multipart/form-data' }
+    opts = request_options(body: body, headers: headers)
+    res = request(:post, url, opts)
+    res['fileKey']
+  end
+
+  private
+
+  def connection_builder(&block)
+    lambda { |con|
+      con.request :url_encoded
+      con.request :multipart
+      # NOTE: comment out for avoiding following bug at OAuth2 v1.4.4.
+      #       In 2.x the bug will be fixed.
+      #       refer to https://github.com/oauth-xx/oauth2/pull/380
+      # con.response :json, content_type: /\bjson$/
+      block.call(con) if block_given?
+    }
+  end
+
+  def request(verb, url, opts)
+    response = @access_token.request(verb, url, opts)
+    validate_response(response)
+  rescue OAuth2::Error => e
+    response = e.response
+    raise Kintone::KintoneError.new(response.body, response.status)
+  end
+
+  def validate_response(response, expected_status = 200)
+    if response.status != expected_status
+      raise Kintone::KintoneError.new(response.body, response.status)
+    end
+
+    JSON.parse(response.body)
+  end
+
+  def request_options(params: nil, body: nil, headers: default_headers)
+    opts = {}
+    opts[:headers] = headers
+    opts[:params] = params if params
+    opts[:body] = body if body
+    opts
+  end
+
+  def default_headers
+    { 'Content-Type' => 'application/json' }
+  end
+end
diff --git a/spec/kintone/oauth_api_spec.rb b/spec/kintone/oauth_api_spec.rb
new file mode 100644
index 0000000..9b0c338
--- /dev/null
+++ b/spec/kintone/oauth_api_spec.rb
@@ -0,0 +1,191 @@
+require 'spec_helper'
+
+describe Kintone::OAuthApi do
+  let(:domain) { 'www.example.com' }
+  let(:path) { '/k/v1/path' }
+  let(:token) { 'access_token' }
+  let(:request_verb) { nil }
+  let(:default_request_headers) { { 'Authorization' => "Bearer #{token}" } }
+  let(:option_request_headers) { nil }
+  let(:params) { nil }
+  let(:body) { nil }
+  let(:response_body) { nil }
+  let(:response_status) { 200 }
+
+  let(:add_stub_request) do
+    url = "https://#{domain}#{path}"
+    url += "?#{URI.encode_www_form(params)}" if params && !params.empty?
+
+    stub_request(request_verb, url) \
+      .with do |req|
+        req.body = body.to_json if body
+        headers = default_request_headers
+        headers.merge! option_request_headers if option_request_headers
+        req.headers = headers
+      end
+      .to_return(
+        body: response_body.to_json,
+        status: response_status,
+        headers: { 'Content-type' => 'application/json' }
+      )
+  end
+
+  context 'specify token argument only' do
+    let(:target) { Kintone::OAuthApi.new(domain, token) }
+
+    describe '#get' do
+      before(:each) do
+        add_stub_request
+      end
+      let(:request_verb) { :get }
+      let(:response_body) { { abc: 'def' } }
+      let(:response_status) { 200 }
+      subject { target.get(path, params) }
+
+      context 'with some params' do
+        let(:params) { { 'p1' => 'abc', 'p2' => 'def' } }
+        it { is_expected.to eq 'abc' => 'def' }
+      end
+
+      context 'with empty params' do
+        let(:params) { {} }
+        it { is_expected.to eq 'abc' => 'def' }
+      end
+
+      context 'with nil params' do
+        let(:params) { nil }
+        it { is_expected.to eq 'abc' => 'def' }
+      end
+
+      context 'fail to request when unexpected response status returns' do
+        let(:response_status) { 201 }
+        before(:each) do
+          add_stub_request
+        end
+        it { expect { subject }.to raise_error Kintone::KintoneError }
+      end
+
+      context 'fail to request' do
+        let(:response_status) { 500 }
+        let(:response_body) { { message: '不正なJSON文字列です。', id: '1505999166-897850006', code: 'CB_IJ01' } }
+        before(:each) do
+          add_stub_request
+        end
+        it { expect { subject }.to raise_error Kintone::KintoneError }
+      end
+    end
+
+    describe '#post' do
+      before(:each) do
+        add_stub_request
+      end
+      let(:request_verb) { :post }
+      let(:response_status) { 200 }
+      let(:response_body) { { abc: 'def' } }
+      let(:params) { nil }
+      let(:body) { { p1: 'abc', p2: 'def' } }
+      let(:option_headers) { { 'Content-Type' => 'application/json' } }
+      subject { target.post(path, body) }
+
+      it { is_expected.to eq 'abc' => 'def' }
+    end
+
+    describe '#put' do
+      before(:each) do
+        add_stub_request
+      end
+      let(:request_verb) { :put }
+      let(:response_status) { 200 }
+      let(:response_body) { { abc: 'def' } }
+      let(:params) { nil }
+      let(:body) { { p1: 'abc', p2: 'def' } }
+      let(:option_headers) { { 'Content-Type' => 'application/json' } }
+      subject { target.put(path, body) }
+
+      it { is_expected.to eq 'abc' => 'def' }
+    end
+
+    describe '#delete' do
+      before(:each) do
+        add_stub_request
+      end
+      let(:request_verb) { :delete }
+      let(:response_status) { 200 }
+      let(:response_body) { { abc: 'def' } }
+      let(:params) { nil }
+      let(:body) { { p1: 'abc', p2: 'def' } }
+      let(:option_headers) { { 'Content-Type' => 'application/json' } }
+      subject { target.delete(path, body) }
+
+      it { is_expected.to eq 'abc' => 'def' }
+    end
+
+    describe '#post_file' do
+      before(:each) do
+        add_stub_request
+        expect(Faraday::UploadIO).to receive(:new).with(file_path, content_type, original_filename).and_return(attachment)
+      end
+
+      subject { target.post_file(path, file_path, content_type, original_filename) }
+      let(:file_path) { '/path/to/file.txt' }
+      let(:content_type) { 'text/plain' }
+      let(:original_filename) { 'fileName.txt' }
+      let(:attachment) { double('attachment') }
+      let(:request_verb) { :post }
+      let(:response_status) { 200 }
+      let(:response_body) { { fileKey: 'abc' } }
+      let(:option_headers) { { 'Content-Type' => %r{multipart/form-data} } }
+
+      it { is_expected.to eq 'abc' }
+    end
+
+    describe '#refresh!' do
+      subject { target.refresh! }
+      it { expect { subject }.to raise_error RuntimeError }
+    end
+  end
+
+  context 'specify token and oauth_options arguments' do
+    let(:target) { Kintone::OAuthApi.new(domain, token, oauth_options) }
+    let(:oauth_options) do
+      {
+        client_id: 'client_id',
+        client_secret: 'client_secret',
+        refresh_token: 'refresh_token',
+        expires_at: 1_598_886_000
+      }
+    end
+    let(:access_token_response_body) do
+      {
+        access_token: 'new_access_token',
+        token_type: 'bearer',
+        expires_in: 3600,
+        scope: 'k:app_record:read k:app_record:write k:app_settings:read k:app_settings:write k:file:read k:file:write'
+      }
+    end
+    describe '#refresh!' do
+      before(:each) do
+        url = 'https://www.example.com/oauth2/token'
+        stub_request(:post, url)\
+          .with(
+            body: {
+              client_id: oauth_options[:client_id],
+              client_secret: oauth_options[:client_secret],
+              grant_type: 'refresh_token',
+              refresh_token: oauth_options[:refresh_token]
+            },
+            headers: {
+              'Content-Type': 'application/x-www-form-urlencoded'
+            }
+          )
+          .to_return(
+            body: access_token_response_body.to_json,
+            status: 200,
+            headers: { 'Content-type' => 'application/json' }
+          )
+      end
+      subject { target.refresh!.token }
+      it { is_expected.to eq 'new_access_token' }
+    end
+  end
+end