diff --git a/build.gradle b/build.gradle
index 3aec4cb2..a734401a 100644
--- a/build.gradle
+++ b/build.gradle
@@ -118,5 +118,5 @@ configurations.all {
 
 // ======== wrapper ========
 wrapper {
-	gradleVersion = "4.8.1"
+	gradleVersion = "4.7"
 }
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 758de960..0d4a9516 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index b586949a..16d28051 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,5 @@
-#Fri Jul 27 16:29:08 JST 2018
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.7-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.8.1-all.zip