diff --git a/index.js b/index.js
index df22f06..d7818dd 100644
--- a/index.js
+++ b/index.js
@@ -1,4 +1,14 @@
 'use strict';
 
+/**
+ * 17 の倍数である場合 true を返す
+ * @param {number} num
+ * @returns {boolean}
+ */
+function isMultipleOfSeventeen(num) {
+  return num % 17 === 0;
+}
+
 module.exports = {
+  isMultipleOfSeventeen
 }