diff --git a/README.md b/README.md
index 8f0ce96..d6b10dc 100644
--- a/README.md
+++ b/README.md
@@ -60,6 +60,40 @@ const omitted = $omit(user, ["email"]); // omitted = { id: 1, name: 'John Doe' }
 console.log(omitted.email); // Output: undefined
 ```
 
+```ts
+import { $deepMerge } from "@uchihori/utilities/object";
+
+const target = {
+  a: 1,
+  b: {
+    c: "hello",
+    d: [1, 2],
+  },
+};
+
+const source = {
+  b: {
+    d: [3, 4],
+    e: true,
+  },
+  f: "world",
+};
+
+const merged = $deepMerge(target, source);
+console.log(merged);
+/* Output:
+{
+  a: 1,
+  b: {
+    c: "hello",
+    d: [1, 2, 3, 4],
+    e: true
+  },
+  f: "world"
+}
+*/
+```
+
 ## array
 
 ```ts
@@ -367,3 +401,36 @@ import type { FromPairs } from "./types.ts";
 
 type ObjectFromPairs = FromPairs<[["a", 1], ["b", 2]]>; // { a: 1, b: 2 }
 ```
+
+```ts
+import type { DeepMerge } from "./types.ts";
+
+type A = {
+  a: number;
+  b: {
+    c: string;
+    d: number[];
+  };
+};
+
+type B = {
+  b: {
+    d: boolean[];
+    e: boolean;
+  };
+  f: string;
+};
+
+type Merged = DeepMerge<A, B>;
+/* Result:
+{
+  a: number;
+  b: {
+    c: string;
+    d: (number | boolean)[];
+    e: boolean;
+  };
+  f: string;
+}
+*/
+```
diff --git a/deno.json b/deno.json
index 8c0e5fd..054842b 100644
--- a/deno.json
+++ b/deno.json
@@ -15,5 +15,5 @@
     "@std/assert": "jsr:@std/assert@^0.226.0",
     "@std/testing": "jsr:@std/testing@^0.225.3"
   },
-  "version": "0.5.0"
+  "version": "0.6.0"
 }
diff --git a/object.test.ts b/object.test.ts
index 40dffcc..e268607 100644
--- a/object.test.ts
+++ b/object.test.ts
@@ -1,6 +1,6 @@
 import { assertEquals } from "@std/assert/assert-equals";
 import { assertThrows } from "@std/assert/assert-throws";
-import { $omit, $pick } from "./object.ts";
+import { $deepMerge, $omit, $pick } from "./object.ts";
 
 Deno.test("$pick", () => {
   const obj = { a: "1", b: 2 };
@@ -172,3 +172,69 @@ Deno.test("$omit with invalid arguments", () => {
     "expected an array for a second argument",
   );
 });
+
+Deno.test("$deepMerge", () => {
+  // 基本的なオブジェクトのマージ
+  const obj1 = { a: 1, b: 2 };
+  const obj2 = { b: 3, c: 4 };
+  const merged1 = $deepMerge(obj1, obj2);
+  assertEquals(merged1, { a: 1, b: 3, c: 4 });
+
+  // ネストされたオブジェクトのマージ
+  const nested1 = { a: 1, b: { c: 2, d: 3 } };
+  const nested2 = { b: { d: 4, e: 5 }, f: 6 };
+  const mergedNested = $deepMerge(nested1, nested2);
+  assertEquals(mergedNested, { a: 1, b: { c: 2, d: 4, e: 5 }, f: 6 });
+
+  // 配列のマージ
+  const withArray1 = { a: 1, b: [1, 2, 3] };
+  const withArray2 = { b: [4, 5], c: 3 };
+  const mergedArray = $deepMerge(withArray1, withArray2);
+  assertEquals(mergedArray, { a: 1, b: [1, 2, 3, 4, 5], c: 3 });
+
+  // ネストされた複雑なオブジェクトのマージ
+  const complex1 = { a: 1, b: { c: 2, d: { e: 3, f: 4 } } };
+  const complex2 = { b: { d: { f: 5, g: 6 }, h: 7 } };
+  const mergedComplex = $deepMerge(complex1, complex2);
+  assertEquals(mergedComplex, {
+    a: 1,
+    b: { c: 2, d: { e: 3, f: 5, g: 6 }, h: 7 },
+  });
+
+  // 配列を含むネストされたオブジェクトのマージ
+  const arrayNested1 = { a: { b: [1, 2], c: 3 } };
+  const arrayNested2 = { a: { b: [4, 5], d: 6 } };
+  const mergedArrayNested = $deepMerge(arrayNested1, arrayNested2);
+  assertEquals(mergedArrayNested, { a: { b: [1, 2, 4, 5], c: 3, d: 6 } });
+});
+
+Deno.test("$deepMerge with invalid arguments", () => {
+  // 非オブジェクト引数に対するエラーハンドリング
+  assertThrows(
+    // deno-lint-ignore ban-ts-comment
+    // @ts-ignore
+    () => $deepMerge("not an object", {}),
+    "expected a non-null object for the first argument",
+  );
+
+  assertThrows(
+    // deno-lint-ignore ban-ts-comment
+    // @ts-ignore
+    () => $deepMerge({}, "not an object"),
+    "expected a non-null object for the second argument",
+  );
+
+  assertThrows(
+    // deno-lint-ignore ban-ts-comment
+    // @ts-ignore
+    () => $deepMerge(null, {}),
+    "expected a non-null object for the first argument",
+  );
+
+  assertThrows(
+    // deno-lint-ignore ban-ts-comment
+    // @ts-ignore
+    () => $deepMerge({}, null),
+    "expected a non-null object for the second argument",
+  );
+});
diff --git a/object.ts b/object.ts
index be990f5..f47aaa2 100644
--- a/object.ts
+++ b/object.ts
@@ -59,3 +59,77 @@ export const $omit = <T extends object, E extends keyof T>(
   }
   return result;
 };
+
+import type { DeepMerge } from "./types.ts";
+
+/**
+ * Deeply merges two or more objects.
+ *
+ * @template T - The type of the first object.
+ * @template U - The type of the second object.
+ * @param {T} target - The first object to merge.
+ * @param {U} source - The second object to merge.
+ * @returns {DeepMerge<T, U>} A new object with all properties deeply merged.
+ * @throws Will throw an error if any argument is not a non-null object.
+ */
+export const $deepMerge = <T extends object, U extends object>(
+  target: T,
+  source: U,
+): DeepMerge<T, U> => {
+  // 基本的な検証
+  if (typeof target !== "object" || target === null) {
+    throw new Error("expected a non-null object for the first argument");
+  }
+  if (typeof source !== "object" || source === null) {
+    throw new Error("expected a non-null object for the second argument");
+  }
+
+  // 2つのオブジェクトをマージする内部関数
+  const merge = <A extends object, B extends object>(
+    target: A,
+    source: B,
+  ): DeepMerge<A, B> => {
+    // 結果オブジェクトを作成
+    const result = { ...target } as Record<PropertyKey, unknown>;
+
+    // ソースオブジェクトのプロパティをマージ
+    for (const key in source) {
+      if (Object.prototype.hasOwnProperty.call(source, key)) {
+        const sourceValue = source[key as keyof B];
+        const targetValue = key in target
+          ? (target as Record<string, unknown>)[key]
+          : undefined;
+
+        if (
+          targetValue !== null &&
+          targetValue !== undefined &&
+          sourceValue !== null &&
+          sourceValue !== undefined &&
+          typeof targetValue === "object" &&
+          typeof sourceValue === "object"
+        ) {
+          if (Array.isArray(targetValue) && Array.isArray(sourceValue)) {
+            // 両方が配列の場合はマージ（連結）
+            result[key] = [...targetValue, ...sourceValue] as unknown;
+          } else if (
+            !Array.isArray(targetValue) &&
+            !Array.isArray(sourceValue)
+          ) {
+            // 両方がオブジェクト（配列でない）の場合は再帰的にマージ
+            result[key] = merge(targetValue as object, sourceValue as object);
+          } else {
+            // 一方が配列で一方がオブジェクトの場合はソースの値で上書き
+            result[key] = sourceValue;
+          }
+        } else {
+          // それ以外の場合はソースの値で上書き
+          result[key] = sourceValue;
+        }
+      }
+    }
+
+    return result as DeepMerge<A, B>;
+  };
+
+  return merge(target, source);
+};
diff --git a/type.test.ts b/type.test.ts
index 98ca8e3..5f69510 100644
--- a/type.test.ts
+++ b/type.test.ts
@@ -1,5 +1,6 @@
 import type { AssertTrue, IsExact } from "@std/testing/types";
 import type {
+  DeepMerge,
   FillArray,
   FromPairs,
   IsTuple,
@@ -139,3 +140,50 @@ Deno.test("RemoveItems", () => {
     IsExact<RemoveItems<(number | string)[], 1 | 2 | 3>, (number | string)[]>
   >;
 });
+
+Deno.test("DeepMerge", () => {
+  // 基本的なオブジェクトのマージ
+  type A = { a: number; b: string };
+  type B = { b: boolean; c: number };
+  type ExpectedAB = { a: number; b: boolean; c: number };
+  type _1 = AssertTrue<IsExact<DeepMerge<A, B>, ExpectedAB>>;
+
+  // ネストされたオブジェクトのマージ
+  type C = { a: number; b: { c: string; d: number } };
+  type D = { b: { d: boolean; e: string }; f: number };
+  type ExpectedCD = {
+    a: number;
+    b: { c: string; d: boolean; e: string };
+    f: number;
+  };
+  type _2 = AssertTrue<IsExact<DeepMerge<C, D>, ExpectedCD>>;
+
+  // 配列のマージ
+  type E = { a: number; b: string[]; c: { d: number[] } };
+  type F = { b: boolean[]; c: { d: string[] } };
+  type ExpectedEF = {
+    a: number;
+    b: Array<string | boolean>;
+    c: { d: Array<number | string> };
+  };
+  type _3 = AssertTrue<IsExact<DeepMerge<E, F>, ExpectedEF>>;
+
+  // プリミティブ値の上書き
+  type G = { a: number; b: string };
+  type H = { a: string };
+  type ExpectedGH = { a: string; b: string };
+  type _4 = AssertTrue<IsExact<DeepMerge<G, H>, ExpectedGH>>;
+
+  // 複雑なネストされたオブジェクトのマージ
+  type I = { a: { b: { c: number; d: string }; e: boolean }; f: number[] };
+  type J = { a: { b: { d: number; g: boolean }; h: string }; f: string[] };
+  type ExpectedIJ = {
+    a: {
+      b: { c: number; d: number; g: boolean };
+      e: boolean;
+      h: string;
+    };
+    f: Array<number | string>;
+  };
+  type _5 = AssertTrue<IsExact<DeepMerge<I, J>, ExpectedIJ>>;
+});
diff --git a/types.ts b/types.ts
index 32f2171..4173881 100644
--- a/types.ts
+++ b/types.ts
@@ -216,3 +216,40 @@ export type RemoveItems<T extends Primitive[], U extends Primitive> =
  * Represents primitive types in TypeScript.
  */
 export type Primitive = string | number | boolean | symbol | null | undefined;
+
+/**
+ * Deeply merges two types, recursively combining their properties.
+ *
+ * @template T - The first type to merge.
+ * @template U - The second type to merge.
+ *
+ * @remarks
+ * This type does the following:
+ * 1. If both T and U are objects, it recursively merges their properties.
+ * 2. If either T or U is not an object, U takes precedence.
+ * 3. For arrays, they are merged by creating a union of their element types.
+ *
+ * @example
+ * type A = { a: number; b: { c: string; } };
+ * type B = { b: { d: boolean; }; e: string; };
+ * type Merged = DeepMerge<A, B>;
+ * // { a: number; b: { c: string; d: boolean; }; e: string; }
+ *
+ * @returns A new type representing the deep merge of T and U.
+ */
+export type DeepMerge<T, U> = [T, U] extends [object, object]
+  ? T extends readonly (infer T1)[]
+    ? U extends readonly (infer U1)[] ? Array<T1 | U1> // 配列同士の場合は要素型をマージ
+    : U
+  : U extends readonly (infer U1)[] ? U
+  : {
+    [K in keyof T | keyof U]: K extends keyof U
+      ? K extends keyof T
+        ? T[K] extends object ? U[K] extends object ? DeepMerge<T[K], U[K]>
+          : U[K]
+        : U[K]
+      : U[K]
+      : K extends keyof T ? T[K]
+      : never;
+  }
+  : U;