diff --git a/CHANGELOG.md b/CHANGELOG.md
index b941dd2166..c4956732c1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,7 @@
 ## Unreleased
 
 ### General
--
+- Enhance: セキュリティ向上のため、サインイン時もCAPTCHAを求めるようになりました
 
 ### Client
 - Enhance: ログイン画面の認証フローを改善
diff --git a/packages/frontend/src/components/MkSignin.vue b/packages/frontend/src/components/MkSignin.vue
index 39dc63d3d9..0115f8f494 100644
--- a/packages/frontend/src/components/MkSignin.vue
+++ b/packages/frontend/src/components/MkSignin.vue
@@ -82,6 +82,14 @@ import XPasskey from '@/components/MkSignin.passkey.vue';
 import type { AuthenticationPublicKeyCredential } from '@github/webauthn-json/browser-ponyfill';
 import type { OpenOnRemoteOptions } from '@/scripts/please-login.js';
 
+const captchaFailed = computed((): boolean => {
+	return (
+		instance.enableHcaptcha && !hCaptchaResponse.value ||
+		instance.enableMcaptcha && !mCaptchaResponse.value ||
+		instance.enableRecaptcha && !reCaptchaResponse.value ||
+		instance.enableTurnstile && !turnstileResponse.value);
+});
+
 const emit = defineEmits<{
 	(ev: 'login', v: Misskey.entities.SigninResponse): void;
 }>();
diff --git a/packages/frontend/src/components/MkSignupDialog.form.vue b/packages/frontend/src/components/MkSignupDialog.form.vue
index 4ab4380ad5..38cac7f644 100644
--- a/packages/frontend/src/components/MkSignupDialog.form.vue
+++ b/packages/frontend/src/components/MkSignupDialog.form.vue
@@ -81,10 +81,10 @@ SPDX-License-Identifier: AGPL-3.0-only
 import { ref, computed } from 'vue';
 import { toUnicode } from 'punycode/';
 import * as Misskey from 'misskey-js';
+import * as config from '@@/js/config.js';
 import MkButton from './MkButton.vue';
 import MkInput from './MkInput.vue';
 import MkCaptcha, { type Captcha } from '@/components/MkCaptcha.vue';
-import * as config from '@@/js/config.js';
 import * as os from '@/os.js';
 import { misskeyApi } from '@/scripts/misskey-api.js';
 import { login } from '@/account.js';
@@ -105,6 +105,7 @@ const emit = defineEmits<{
 const host = toUnicode(config.host);
 
 const hcaptcha = ref<Captcha | undefined>();
+const mcaptcha = ref<Captcha | undefined>();
 const recaptcha = ref<Captcha | undefined>();
 const turnstile = ref<Captcha | undefined>();
 
@@ -281,6 +282,7 @@ async function onSubmit(): Promise<void> {
 	} catch {
 		submitting.value = false;
 		hcaptcha.value?.reset?.();
+		mcaptcha.value?.reset?.();
 		recaptcha.value?.reset?.();
 		turnstile.value?.reset?.();