diff --git a/gatsby-config.js b/gatsby-config.js
index 81a7192..8530850 100644
--- a/gatsby-config.js
+++ b/gatsby-config.js
@@ -3,7 +3,7 @@ module.exports = {
     title: `國立臺灣師範大學附屬高級中學`,
     titleTemplate: "%s | hsnu.org",
     description: `國立臺灣師範大學附屬高級中學，簡稱為HSNU，是一所位處臺北市大安區信義的高級中學，附屬於國立臺灣師範大學。`,
-    siteUrl: "https://hsnu.org", // No trailing slash allowed!
+    siteUrl: `${process.env.SITE_URL}`, // No trailing slash allowed!
     image: "https://upload.wikimedia.org/wikipedia/commons/thumb/a/a8/The_Main_Gate_of_The_Affiliated_Senior_High_School_of_NTNU.jpg/1024px-The_Main_Gate_of_The_Affiliated_Senior_High_School_of_NTNU.jpg",
   },
   plugins: [
@@ -76,15 +76,15 @@ module.exports = {
     {
       resolve: `gatsby-plugin-canonical-urls`,
       options: {
-        siteUrl: `https://hsnu.org`,
+        siteUrl: `${process.env.SITE_URL}`,
       },
     },
     // robot.txt
     {
       resolve: "gatsby-plugin-robots-txt",
       options: {
-        host: "https://hsnu.org",
-        sitemap: "https://hsnu.org/sitemap.xml",
+        host: `${process.env.SITE_URL}`,
+        sitemap: `${process.env.SITE_URL}/sitemap.xml`,
         policy: [{ userAgent: "*", allow: "/" }],
       },
     },
diff --git a/src/components/layout/Header.js b/src/components/layout/Header.js
index 319af5d..3948e08 100644
--- a/src/components/layout/Header.js
+++ b/src/components/layout/Header.js
@@ -20,11 +20,11 @@ export const Header = () => {
     },
     {
       name: "行事曆",
-      url: "https://hsnu.org/search/?search=%E8%A1%8C%E4%BA%8B%E6%9B%86",
+      url: `${process.env.SITE_URL}/search/?search=%E8%A1%8C%E4%BA%8B%E6%9B%86`,
     },
     {
       name: "段考",
-      url: "https://hsnu.org/search?search=%E6%AE%B5%E8%80%83",
+      url: `${process.env.SITE_URL}/search?search=%E6%AE%B5%E8%80%83`,
     },
     {
       name: "國中部",