diff --git a/omnibox/background.ts b/omnibox/background.ts
index 973aa36..821d972 100644
--- a/omnibox/background.ts
+++ b/omnibox/background.ts
@@ -15,6 +15,7 @@ import { Asearch } from "./deps/asearch.ts";
 import { browser } from "./deps/webextension.ts";
 import { ensureTabId } from "./utils.ts";
 import { getData } from "./storage.ts";
+import { isURL } from "./isURL.ts";
 
 //
 // browserActionボタンを押したときcontent_script.jsにメッセージを送る
@@ -80,10 +81,12 @@ function search(
 // ユーザがメニューを選択したとき呼ばれるもの
 //
 browser.omnibox.onInputEntered.addListener(async (text) => {
-  if (text.match(/^http/)) {
+  if (isURL(text)) {
     browser.tabs.update({ url: text });
   } else {
-    const response = await fetch("https://goquick.org", { credentials: "include"}); // GoQuick.orgユーザはGoQuick.orgを利用
+    const response = await fetch("https://goquick.org", {
+      credentials: "include",
+    }); // GoQuick.orgユーザはGoQuick.orgを利用
     const data = await response.text();
     browser.tabs.update({
       url: data.match("GoQuick Login")
diff --git a/omnibox/deps/testing.ts b/omnibox/deps/testing.ts
new file mode 100644
index 0000000..89ab027
--- /dev/null
+++ b/omnibox/deps/testing.ts
@@ -0,0 +1 @@
+export * from "https://deno.land/std@0.126.0/testing/asserts.ts";
diff --git a/omnibox/isURL.test.ts b/omnibox/isURL.test.ts
new file mode 100644
index 0000000..7be608c
--- /dev/null
+++ b/omnibox/isURL.test.ts
@@ -0,0 +1,11 @@
+/// <reference lib="deno.ns" />
+import { isURL } from "./isURL.ts";
+import { assert } from "./deps/testing.ts";
+
+Deno.test("isURL()", () => {
+  assert(isURL("https://example.com"));
+  assert(isURL("http://goquick.org"));
+  assert(isURL("file:///users/file.txt"));
+  assert(isURL("things:///show?id=xxx"));
+  assert(!isURL("helpfeel"));
+});
diff --git a/omnibox/isURL.ts b/omnibox/isURL.ts
new file mode 100644
index 0000000..45259ce
--- /dev/null
+++ b/omnibox/isURL.ts
@@ -0,0 +1,10 @@
+/** URLかどうか判定する */
+export function isURL(text: string): boolean {
+  try {
+    new URL(text);
+    return true;
+  } catch (e: unknown) {
+    if (e instanceof TypeError) return false;
+    throw e;
+  }
+}