diff --git a/docs/1-trial-session/08-loop/_samples/is-prime-using-and/script.js b/docs/1-trial-session/08-loop/_samples/is-prime-using-and/script.js
index 0e64e2f02..f347ef983 100644
--- a/docs/1-trial-session/08-loop/_samples/is-prime-using-and/script.js
+++ b/docs/1-trial-session/08-loop/_samples/is-prime-using-and/script.js
@@ -1,4 +1,4 @@
-let n = 89; //任意の整数
+const n = 89; //任意の整数
 
 let isPrime = true;
 if (n <= 1) {
diff --git a/docs/1-trial-session/08-loop/_samples/is-prime/script.js b/docs/1-trial-session/08-loop/_samples/is-prime/script.js
index 5fe70f196..f3d73def7 100644
--- a/docs/1-trial-session/08-loop/_samples/is-prime/script.js
+++ b/docs/1-trial-session/08-loop/_samples/is-prime/script.js
@@ -1,4 +1,4 @@
-let n = 57; // 任意の整数
+const n = 57; // 任意の整数
 
 let isPrime = true;
 if (n <= 1) {
diff --git a/docs/1-trial-session/08-loop/index.md b/docs/1-trial-session/08-loop/index.md
index a2135bc2a..27dbe0f40 100644
--- a/docs/1-trial-session/08-loop/index.md
+++ b/docs/1-trial-session/08-loop/index.md
@@ -248,7 +248,7 @@ document.write(product);
 変数の、最後に代入した値のみを保持する性質を利用します。
 
 ```javascript
-let n = 57; // 任意の整数
+const n = 57; // 任意の整数
 
 let isPrime = true;
 if (n <= 1) {
@@ -276,7 +276,7 @@ if (isPrime) {
 前項で割ったあまりが0でないこととの `&&` (AND) をとることで帰納的に求めることもできます。
 
 ```javascript
-let n = 89; // 任意の整数
+const n = 89; // 任意の整数
 
 let isPrime = true;
 if (n <= 1) {