diff --git a/express/eslint.config.js b/express/eslint.config.js
index c067f1e3..81638ddd 100644
--- a/express/eslint.config.js
+++ b/express/eslint.config.js
@@ -11,8 +11,6 @@ export default [
 	{
 		files: ['src/app.ts'],
 		rules: {
-			'no-console': 'off',
-			'@typescript-eslint/no-misused-promises': 'off',
 			'@typescript-eslint/no-unsafe-call': 'off', // Github Actions 環境ではエラーになる
 		},
 	},
diff --git a/express/package.json b/express/package.json
index f1293893..6dcfe3ac 100644
--- a/express/package.json
+++ b/express/package.json
@@ -17,6 +17,7 @@
 		"dotenv": "^16.4.7",
 		"express": "^5.0.1",
 		"htpasswd-js": "^1.0.2",
+		"log4js": "^6.9.1",
 		"matcher": "^5.0.0"
 	},
 	"devDependencies": {
diff --git a/express/src/app.ts b/express/src/app.ts
index 1fae4729..7445bf3a 100644
--- a/express/src/app.ts
+++ b/express/src/app.ts
@@ -6,6 +6,7 @@ import * as dotenv from 'dotenv';
 import express, { type NextFunction, type Request, type Response } from 'express';
 // @ts-expect-error: ts(7016)
 import htpasswd from 'htpasswd-js';
+import Log4js from 'log4js';
 import { isMatch } from 'matcher';
 import HtmlEscape from '@w0s/html-escape';
 // @ts-expect-error: ts(7016)
@@ -13,11 +14,15 @@ import { handler as ssrHandler } from '@w0s.jp/astro/dist/server/entry.mjs';
 import config from './config/express.js';
 import { env } from './util/env.js';
 
-/* 設定ファイル読み込み */
 dotenv.config({
 	path: process.env['NODE_ENV'] === 'production' ? '../.env.production' : '../.env.development',
 });
 
+/* Logger */
+Log4js.configure(env('LOGGER'));
+const logger = Log4js.getLogger();
+
+/* Express */
 const app = express();
 
 app.set('x-powered-by', false);
@@ -153,7 +158,7 @@ app.use(
 					.find(([fileExtension]) => fileExtension === extensionOrigin)
 					?.at(1);
 			if (mimeType === undefined) {
-				console.warn(`MIME type is undefined: ${requestUrlOrigin}`);
+				logger.error(`MIME type is undefined: ${requestUrlOrigin}`);
 			}
 			res.setHeader('Content-Type', mimeType ?? 'application/octet-stream');
 
@@ -192,31 +197,25 @@ app.use(
 	}),
 );
 
-/**
- * SSR
- */
+/* SSR */
 app.use(async (req, res, next): Promise<void> => {
 	await ssrHandler(req, res, next);
 });
 
-/**
- * エラー処理
- */
+/* Error pages */
 app.use((req, res): void => {
-	console.warn(`404 Not Found: ${req.method} ${req.url}`);
+	logger.warn(`404 Not Found: ${req.method} ${req.url}`);
 
 	res.status(404).sendFile(path.resolve(`${config.static.root}/404.html`));
 });
 app.use((err: Error, req: Request, res: Response, _next: NextFunction /* eslint-disable-line @typescript-eslint/no-unused-vars */): void => {
-	console.error(`${req.method} ${req.url}`, err.stack);
+	logger.fatal(`${req.method} ${req.url}`, err.stack);
 
 	res.status(500).sendFile(path.resolve(`${config.static.root}/500.html`));
 });
 
-/**
- * HTTP サーバー起動
- */
+/* HTTP Server */
 const port = env('PORT', 'number');
 app.listen(port, () => {
-	console.info(`Server is running on http://localhost:${String(port)}`);
+	logger.info(`Server is running on http://localhost:${String(port)}`);
 });
diff --git a/package-lock.json b/package-lock.json
index b55ba97d..497e5a3f 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2706,6 +2706,7 @@
 				"dotenv": "^16.4.7",
 				"express": "^5.0.1",
 				"htpasswd-js": "^1.0.2",
+				"log4js": "^6.9.1",
 				"matcher": "^5.0.0"
 			},
 			"devDependencies": {
@@ -7737,6 +7738,7 @@
 			"version": "4.0.14",
 			"resolved": "https://registry.npmjs.org/date-format/-/date-format-4.0.14.tgz",
 			"integrity": "sha512-39BOQLs9ZjKh0/patS9nrT8wc3ioX3/eA/zgbKNopnF2wCqJEoxywwwElATYvRsXdnOxA/OQeQoFZ3rFjVajhg==",
+			"license": "MIT",
 			"engines": {
 				"node": ">=4.0"
 			}
@@ -11408,6 +11410,7 @@
 			"version": "6.9.1",
 			"resolved": "https://registry.npmjs.org/log4js/-/log4js-6.9.1.tgz",
 			"integrity": "sha512-1somDdy9sChrr9/f4UlzhdaGfDR2c/SaD2a4T7qEkG4jTS57/B3qmnjLYePwQ8cqWnUHZI0iAKxMBpCZICiZ2g==",
+			"license": "Apache-2.0",
 			"dependencies": {
 				"date-format": "^4.0.14",
 				"debug": "^4.3.4",
@@ -14648,7 +14651,8 @@
 		"node_modules/rfdc": {
 			"version": "1.4.1",
 			"resolved": "https://registry.npmjs.org/rfdc/-/rfdc-1.4.1.tgz",
-			"integrity": "sha512-q1b3N5QkRUWUl7iyylaaj3kOpIT0N2i9MqIEQXP73GVsN9cw3fdx8X63cEmWhJGi2PPCF23Ijp7ktmd39rawIA=="
+			"integrity": "sha512-q1b3N5QkRUWUl7iyylaaj3kOpIT0N2i9MqIEQXP73GVsN9cw3fdx8X63cEmWhJGi2PPCF23Ijp7ktmd39rawIA==",
+			"license": "MIT"
 		},
 		"node_modules/rimraf": {
 			"version": "3.0.2",
@@ -15447,6 +15451,7 @@
 			"version": "3.1.5",
 			"resolved": "https://registry.npmjs.org/streamroller/-/streamroller-3.1.5.tgz",
 			"integrity": "sha512-KFxaM7XT+irxvdqSP1LGLgNWbYN7ay5owZ3r/8t77p+EtSUAfUgtl7be3xtqtOmGUl9K9YPO2ca8133RlTjvKw==",
+			"license": "MIT",
 			"dependencies": {
 				"date-format": "^4.0.14",
 				"debug": "^4.3.4",
@@ -15460,6 +15465,7 @@
 			"version": "8.1.0",
 			"resolved": "https://registry.npmjs.org/fs-extra/-/fs-extra-8.1.0.tgz",
 			"integrity": "sha512-yhlQgA6mnOJUKOsRUFsgJdQCvkKhcz8tlZG5HBQfReYZy46OwLcY+Zia0mtdHsOo9y/hP+CxMN0TU9QxoOtG4g==",
+			"license": "MIT",
 			"dependencies": {
 				"graceful-fs": "^4.2.0",
 				"jsonfile": "^4.0.0",
@@ -15473,6 +15479,7 @@
 			"version": "4.0.0",
 			"resolved": "https://registry.npmjs.org/jsonfile/-/jsonfile-4.0.0.tgz",
 			"integrity": "sha512-m6F1R3z8jjlf2imQHS2Qez5sjKWQzbuuhuJ/FKYFRZvPE3PuHcSMVZzfsLhGVOkfd20obL5SWEBew5ShlquNxg==",
+			"license": "MIT",
 			"optionalDependencies": {
 				"graceful-fs": "^4.1.6"
 			}
@@ -15481,6 +15488,7 @@
 			"version": "0.1.2",
 			"resolved": "https://registry.npmjs.org/universalify/-/universalify-0.1.2.tgz",
 			"integrity": "sha512-rBJeI5CXAlmy1pV+617WB9J63U6XcazHHF2f2dbJix4XzpUF0RS3Zbj0FGIOCAva5P/d/GBOYaACQ1w+0azUkg==",
+			"license": "MIT",
 			"engines": {
 				"node": ">= 4.0.0"
 			}