diff --git a/src/interpreter/deep-equal.ts b/src/interpreter/deep-equal.ts
new file mode 100644
index 00000000..c3fc8b13
--- /dev/null
+++ b/src/interpreter/deep-equal.ts
@@ -0,0 +1,71 @@
+export function deepEqual(a: unknown, b: unknown): boolean {
+	return deepEqualRefs(a, b, [], []);
+}
+
+function deepEqualRefs(a: unknown, b: unknown, refsA: unknown[], refsB: unknown[]): boolean {
+	// プリミティブ値や参照の比較
+	// NOTE: Object.is()はNaN同士の比較でもtrue
+	if (Object.is(a, b)) return true;
+
+	// Object (a、b共にnullは含まない)
+	if (a !== null && b !== null && typeof a === 'object' && typeof b === 'object') {
+		// 参照の循環をチェック
+		// 両方の循環が確認された時点で、その先も一致すると保証できるためtrueで返す
+		const indexA = refsA.findIndex(x => x === a);
+		const indexB = refsB.findIndex(x => x === b);
+		if (indexA !== -1 && indexB !== -1) {
+			return true;
+		}
+
+		// 次の参照パスを生成
+		const nextRefsA = [...refsA, a];
+		const nextRefsB = [...refsB, b];
+
+		// Array
+		if (Array.isArray(a) && Array.isArray(b)) {
+			if (a.length !== b.length) return false;
+			for (let i = 0; i < a.length; i++) {
+				if (!deepEqualRefs(a[i], b[i], nextRefsA, nextRefsB)) return false;
+			}
+			return true;
+		}
+
+		// Map
+		if (a instanceof Map && b instanceof Map) {
+			if (a.size !== b.size) return false;
+			const aEntries = a.entries();
+			const bEntries = b.entries();
+			for (let i = 0; i < a.size; i++) {
+				const entryA = aEntries.next();
+				const entryB = bEntries.next();
+				if (!deepEqualRefs(entryA.value[0], entryB.value[0], nextRefsA, nextRefsB)) return false;
+				if (!deepEqualRefs(entryA.value[1], entryB.value[1], nextRefsA, nextRefsB)) return false;
+			}
+			return true;
+		}
+
+		// Set
+		if (a instanceof Set && b instanceof Set) {
+			if (a.size !== b.size) return false;
+			const aValues = a.values();
+			const bValues = b.values();
+			for (let i = 0; i < a.size; i++) {
+				const valueA = aValues.next();
+				const valueB = bValues.next();
+				if (!deepEqualRefs(valueA.value, valueB.value, nextRefsA, nextRefsB)) return false;
+			}
+			return true;
+		}
+
+		// object keys
+		const keysA = Object.keys(a);
+		const keysB = Object.keys(b);
+		if (keysA.length !== keysB.length) return false;
+		for (const key of keysA) {
+			if (!deepEqualRefs((a as Record<string, unknown>)[key], (b as Record<string, unknown>)[key], nextRefsA, nextRefsB)) return false;
+		}
+		return true;
+	}
+
+	return false;
+}
diff --git a/test/deep-equal.ts b/test/deep-equal.ts
new file mode 100644
index 00000000..f84ee3b6
--- /dev/null
+++ b/test/deep-equal.ts
@@ -0,0 +1,92 @@
+import * as assert from 'assert';
+import { deepEqual } from '../src/interpreter/deep-equal';
+
+describe('compare', () => {
+	test('object and object', () => {
+		assert.strictEqual(deepEqual({ a: 1 }, { a: 1 }), true);
+		assert.strictEqual(deepEqual({ a: 1 }, { a: 2 }), false);
+		assert.strictEqual(deepEqual({ a: 1 }, { a: 1, b: 2 }), false);
+	});
+
+	test('number and number', () => {
+		assert.strictEqual(deepEqual(1, 1), true);
+		assert.strictEqual(deepEqual(1, 2), false);
+	});
+
+	test('number[] and number[]', () => {
+		assert.strictEqual(deepEqual([1, 2, 3], [1, 2, 3]), true);
+		assert.strictEqual(deepEqual([1, 2, 3], [4, 5, 6]), false);
+		assert.strictEqual(deepEqual([1, 2], [1, 2, 3]), false);
+		assert.strictEqual(deepEqual([1, 2, 3], [1, 2]), false);
+	});
+
+	test('string[] and string[]', () => {
+		assert.strictEqual(deepEqual(['a', 'b', 'c'], ['a', 'b', 'c']), true);
+		assert.strictEqual(deepEqual(['a', 'b', 'c'], ['x', 'y', 'z']), false);
+		assert.strictEqual(deepEqual(['a', 'b'], ['a', 'b', 'c']), false);
+		assert.strictEqual(deepEqual(['a', 'b', 'c'], ['a', 'b']), false);
+	});
+
+	test('object and null', () => {
+		assert.strictEqual(deepEqual({ a: 1 }, null), false);
+	});
+});
+
+test('null, undefined, NaN', () => {
+	assert.strictEqual(deepEqual(null, null), true);
+	assert.strictEqual(deepEqual(undefined, undefined), true);
+	assert.strictEqual(deepEqual(NaN, NaN), true);
+	assert.strictEqual(deepEqual(null, undefined), false);
+	assert.strictEqual(deepEqual(null, NaN), false);
+	assert.strictEqual(deepEqual(undefined, NaN), false);
+});
+
+describe('recursive', () => {
+	test('simple', () => {
+		let x: any = { n: null };
+		x.n = x;
+		let y: any = { n: null };
+		y.n = y;
+		assert.strictEqual(deepEqual(x, y), true);
+	});
+
+	test('object', () => {
+		let x: any = { a: { b: { a: null } } };
+		x.a.b.a = x.a;
+		let y: any = { a: { b: null } };
+		y.a.b = y;
+		assert.strictEqual(deepEqual(x, y), true);
+	});
+
+	test('object 2', () => {
+		let x: any = { a: { b: { a: null } } };
+		x.a.b.a = x.a;
+		let y: any = { a: { b: null } };
+		y.a.b = y.a;
+		assert.strictEqual(deepEqual(x, y), false);
+	});
+
+	test('different path of object', () => {
+		let x: any = { a: { b: null } };
+		x.a.b = x;
+		let y: any = { a: { b: { a: { b: { a: null } } } } };
+		y.a.b.a.b.a = y.a.b.a;
+		assert.strictEqual(deepEqual(x, y), true);
+	});
+
+	test('different path of object 2', () => {
+		let x: any = { a: { b: null } };
+		x.a.b = x;
+		let y: any = { a: { b: { a: { b: { a: null } } } } };
+		y.a.b.a.b.a = y.a.b;
+		assert.strictEqual(deepEqual(x, y), false);
+	});
+
+	test('object and array', () => {
+		let a: any = [{ a: [] }];
+		let b: any = [{ a: [] }];
+		a[0].a[0] = a;
+		b[0].a[0] = b[0];
+		assert.strictEqual(deepEqual(a, b), false);
+	});
+});