diff --git a/src/interpreter/index.ts b/src/interpreter/index.ts
index 8423791d..1ea3d16c 100644
--- a/src/interpreter/index.ts
+++ b/src/interpreter/index.ts
@@ -258,6 +258,9 @@ export class Interpreter {
 
 					const value = await this._eval(node.expr, nsScope, []);
 					assertValue(value);
+
+					await this.evalAndSetAttr(node.attr, value, scope, []);
+
 					if (
 						node.expr.type === 'fn'
 						&& isFunction(value)
@@ -302,6 +305,9 @@ export class Interpreter {
 
 					const value = this._evalSync(node.expr, nsScope, []);
 					assertValue(value);
+
+					this.evalAndSetAttrSync(node.attr, value, scope, []);
+
 					if (
 						node.expr.type === 'fn'
 						&& isFunction(value)
@@ -648,18 +654,7 @@ export class Interpreter {
 				if (isControl(value)) {
 					return value;
 				}
-				if (node.attr.length > 0) {
-					const attrs: Value['attr'] = [];
-					for (const nAttr of node.attr) {
-						const value = await this._eval(nAttr.value, scope, callStack);
-						assertValue(value);
-						attrs.push({
-							name: nAttr.name,
-							value,
-						});
-					}
-					value.attr = attrs;
-				}
+				await this.evalAndSetAttr(node.attr, value, scope, callStack);
 				if (
 					node.expr.type === 'fn'
 					&& node.dest.type === 'identifier'
@@ -1192,18 +1187,7 @@ export class Interpreter {
 				if (isControl(value)) {
 					return value;
 				}
-				if (node.attr.length > 0) {
-					const attrs: Value['attr'] = [];
-					for (const nAttr of node.attr) {
-						const value = this._evalSync(nAttr.value, scope, callStack);
-						assertValue(value);
-						attrs.push({
-							name: nAttr.name,
-							value,
-						});
-					}
-					value.attr = attrs;
-				}
+				this.evalAndSetAttrSync(node.attr, value, scope, callStack);
 				if (
 					node.expr.type === 'fn'
 					&& node.dest.type === 'identifier'
@@ -1666,6 +1650,38 @@ export class Interpreter {
 		this.unpauseHandlers = [];
 	}
 
+	@autobind
+	private async evalAndSetAttr(attr: Ast.Attribute[], value: Value, scope: Scope, callStack: readonly CallInfo[]): Promise<void> {
+		if (attr.length > 0) {
+			const attrs: Value['attr'] = [];
+			for (const nAttr of attr) {
+				const value = await this._eval(nAttr.value, scope, callStack);
+				assertValue(value);
+				attrs.push({
+					name: nAttr.name,
+					value,
+				});
+			}
+			value.attr = attrs;
+		}
+	}
+
+	@autobind
+	private evalAndSetAttrSync(attr: Ast.Attribute[], value: Value, scope: Scope, callStack: readonly CallInfo[]): void {
+		if (attr.length > 0) {
+			const attrs: Value['attr'] = [];
+			for (const nAttr of attr) {
+				const value = this._evalSync(nAttr.value, scope, callStack);
+				assertValue(value);
+				attrs.push({
+					name: nAttr.name,
+					value,
+				});
+			}
+			value.attr = attrs;
+		}
+	}
+
 	@autobind
 	private define(scope: Scope, dest: Ast.Expression, value: Value, isMutable: boolean): void {
 		switch (dest.type) {
diff --git a/test/interpreter.ts b/test/interpreter.ts
index bcf9e64d..0b8bc0ea 100644
--- a/test/interpreter.ts
+++ b/test/interpreter.ts
@@ -1,6 +1,7 @@
 import * as assert from 'assert';
 import { describe, expect, test, vi, beforeEach, afterEach } from 'vitest';
 import { Parser, Interpreter, values, errors, utils, Ast } from '../src';
+import { FALSE, NUM, OBJ, STR, TRUE, Value } from '../src/interpreter/value';
 
 let { FN_NATIVE } = values;
 let { AiScriptRuntimeError, AiScriptIndexOutOfRangeError, AiScriptHostsideError } = errors;
@@ -324,3 +325,61 @@ describe('pause', () => {
 		});
 	});
 });
+
+describe('Attribute', () => {
+	const getAttr = async (name: string, script: string): Promise<Value['attr']> => {
+		const parser = new Parser();
+		const interpreter = new Interpreter({});
+		const ast = parser.parse(script);
+		await interpreter.exec(ast);
+		const value = interpreter.scope.get(name);
+		return value.attr;
+	};
+
+	test.concurrent('no attribute', async () => {
+		const attr = await getAttr('f', `
+		@f() {}
+		`);
+		expect(attr).toBeUndefined();
+	});
+
+	test.concurrent('single attribute', async () => {
+		const attr = await getAttr('f', `
+		#[x 42]
+		@f() {}
+		`);
+		expect(attr).toStrictEqual([{ name: 'x', value: NUM(42) }]);
+	});
+
+	test.concurrent('multiple attributes', async () => {
+		const attr = await getAttr('f', `
+		#[o { a: 1, b: 2 }]
+		#[s "ai"]
+		#[b false]
+		@f() {}
+		`);
+		expect(attr).toStrictEqual([
+			{ name: 'o', value: OBJ(new Map([['a', NUM(1)], ['b', NUM(2)]])) },
+			{ name: 's', value: STR('ai') },
+			{ name: 'b', value: FALSE },
+		]);
+	});
+
+	test.concurrent('single attribute without value', async () => {
+		const attr = await getAttr('f', `
+		#[x]
+		@f() {}
+		`);
+		expect(attr).toStrictEqual([{ name: 'x', value: TRUE }]);
+	});
+
+	test.concurrent('attribute under namespace', async () => {
+		const attr = await getAttr('Ns:f', `
+		:: Ns {
+			#[x 42]
+			@f() {}
+		}
+		`);
+		expect(attr).toStrictEqual([{ name: 'x', value: NUM(42) }]);
+	});
+});
diff --git a/unreleased/fix-attr-in-ns-not-evaluated.md b/unreleased/fix-attr-in-ns-not-evaluated.md
new file mode 100644
index 00000000..25c80fe2
--- /dev/null
+++ b/unreleased/fix-attr-in-ns-not-evaluated.md
@@ -0,0 +1 @@
+- Fix: 名前空間内において属性の値が評価されない問題を修正