diff --git a/Dockerfile.template.erb b/Dockerfile.template.erb
index 695b699..91e2d8c 100644
--- a/Dockerfile.template.erb
+++ b/Dockerfile.template.erb
@@ -120,6 +120,11 @@ RUN apt-get update \
  && gem install async -v 1.32.1 \
  && gem install async-http -v 0.64.2 \
  && gem install fluentd -v <%= fluentd_ver %> \
+ && export GEM_DIR=$(ruby -e 'puts Gem.dir') \
+ && echo GEM_DIR=$GEM_DIR \
+ && rm -rf $GEM_DIR/cache/*.gem \
+ && find $GEM_DIR -type d -name test -or -name ext -or -name spec -or -name benchmark | xargs -r rm -rf \
+ && find $GEM_DIR -name "*.so" | xargs -r strip \
 <% if is_alpine %>
  && gem install bigdecimal -v 1.4.4 \
  && apk del .build-deps \
@@ -146,7 +151,7 @@ RUN apt-get update \
                   '*-dev' \
  && rm -rf /var/lib/apt/lists/* \
 <% end %>
- && rm -rf /tmp/* /var/tmp/* /usr/lib/ruby/gems/*/cache/*.gem /usr/lib/ruby/gems/3.*/gems/fluentd-*/test
+ && rm -rf /tmp/* /var/tmp/*
 
 <% if is_alpine %>
 RUN addgroup -S fluent && adduser -S -G fluent fluent \
diff --git a/v1.17/alpine/Dockerfile b/v1.17/alpine/Dockerfile
index ab417b1..53b5b94 100644
--- a/v1.17/alpine/Dockerfile
+++ b/v1.17/alpine/Dockerfile
@@ -23,10 +23,15 @@ RUN apk update \
  && gem install async -v 1.32.1 \
  && gem install async-http -v 0.64.2 \
  && gem install fluentd -v 1.17.1 \
+ && export GEM_DIR=$(ruby -e 'puts Gem.dir') \
+ && echo GEM_DIR=$GEM_DIR \
+ && rm -rf $GEM_DIR/cache/*.gem \
+ && find $GEM_DIR -type d -name test -or -name ext -or -name spec -or -name benchmark | xargs -r rm -rf \
+ && find $GEM_DIR -name "*.so" | xargs -r strip \
  && gem install bigdecimal -v 1.4.4 \
  && apk del .build-deps \
  && rm -rf /var/cache/apk/* \
- && rm -rf /tmp/* /var/tmp/* /usr/lib/ruby/gems/*/cache/*.gem /usr/lib/ruby/gems/3.*/gems/fluentd-*/test
+ && rm -rf /tmp/* /var/tmp/*
 
 RUN addgroup -S fluent && adduser -S -G fluent fluent \
     # for log storage (maybe shared with host)
diff --git a/v1.17/arm64/debian/Dockerfile b/v1.17/arm64/debian/Dockerfile
index ed0b6be..c79f84e 100644
--- a/v1.17/arm64/debian/Dockerfile
+++ b/v1.17/arm64/debian/Dockerfile
@@ -35,6 +35,11 @@ RUN apt-get update \
  && gem install async -v 1.32.1 \
  && gem install async-http -v 0.64.2 \
  && gem install fluentd -v 1.17.1 \
+ && export GEM_DIR=$(ruby -e 'puts Gem.dir') \
+ && echo GEM_DIR=$GEM_DIR \
+ && rm -rf $GEM_DIR/cache/*.gem \
+ && find $GEM_DIR -type d -name test -or -name ext -or -name spec -or -name benchmark | xargs -r rm -rf \
+ && find $GEM_DIR -name "*.so" | xargs -r strip \
  && dpkgArch="$(dpkg --print-architecture | awk -F- '{ print $NF }')" \
  && wget -O /usr/local/bin/tini "https://github.com/krallin/tini/releases/download/v$TINI_VERSION/tini-$dpkgArch" \
  && wget -O /usr/local/bin/tini.asc "https://github.com/krallin/tini/releases/download/v$TINI_VERSION/tini-$dpkgArch.asc" \
@@ -55,7 +60,7 @@ RUN apt-get update \
                   $buildDeps \
                   '*-dev' \
  && rm -rf /var/lib/apt/lists/* \
- && rm -rf /tmp/* /var/tmp/* /usr/lib/ruby/gems/*/cache/*.gem /usr/lib/ruby/gems/3.*/gems/fluentd-*/test
+ && rm -rf /tmp/* /var/tmp/*
 
 RUN groupadd -r fluent && useradd -r -g fluent fluent \
     # for log storage (maybe shared with host)
diff --git a/v1.17/armhf/debian/Dockerfile b/v1.17/armhf/debian/Dockerfile
index 6375ee8..02d2550 100644
--- a/v1.17/armhf/debian/Dockerfile
+++ b/v1.17/armhf/debian/Dockerfile
@@ -35,6 +35,11 @@ RUN apt-get update \
  && gem install async -v 1.32.1 \
  && gem install async-http -v 0.64.2 \
  && gem install fluentd -v 1.17.1 \
+ && export GEM_DIR=$(ruby -e 'puts Gem.dir') \
+ && echo GEM_DIR=$GEM_DIR \
+ && rm -rf $GEM_DIR/cache/*.gem \
+ && find $GEM_DIR -type d -name test -or -name ext -or -name spec -or -name benchmark | xargs -r rm -rf \
+ && find $GEM_DIR -name "*.so" | xargs -r strip \
  && dpkgArch="$(dpkg --print-architecture | awk -F- '{ print $NF }')" \
  && wget -O /usr/local/bin/tini "https://github.com/krallin/tini/releases/download/v$TINI_VERSION/tini-$dpkgArch" \
  && wget -O /usr/local/bin/tini.asc "https://github.com/krallin/tini/releases/download/v$TINI_VERSION/tini-$dpkgArch.asc" \
@@ -55,7 +60,7 @@ RUN apt-get update \
                   $buildDeps \
                   '*-dev' \
  && rm -rf /var/lib/apt/lists/* \
- && rm -rf /tmp/* /var/tmp/* /usr/lib/ruby/gems/*/cache/*.gem /usr/lib/ruby/gems/3.*/gems/fluentd-*/test
+ && rm -rf /tmp/* /var/tmp/*
 
 RUN groupadd -r fluent && useradd -r -g fluent fluent \
     # for log storage (maybe shared with host)
diff --git a/v1.17/debian/Dockerfile b/v1.17/debian/Dockerfile
index 4a245d1..bd113d2 100644
--- a/v1.17/debian/Dockerfile
+++ b/v1.17/debian/Dockerfile
@@ -24,6 +24,11 @@ RUN apt-get update \
  && gem install async -v 1.32.1 \
  && gem install async-http -v 0.64.2 \
  && gem install fluentd -v 1.17.1 \
+ && export GEM_DIR=$(ruby -e 'puts Gem.dir') \
+ && echo GEM_DIR=$GEM_DIR \
+ && rm -rf $GEM_DIR/cache/*.gem \
+ && find $GEM_DIR -type d -name test -or -name ext -or -name spec -or -name benchmark | xargs -r rm -rf \
+ && find $GEM_DIR -name "*.so" | xargs -r strip \
  && dpkgArch="$(dpkg --print-architecture | awk -F- '{ print $NF }')" \
  && wget -O /usr/local/bin/tini "https://github.com/krallin/tini/releases/download/v$TINI_VERSION/tini-$dpkgArch" \
  && wget -O /usr/local/bin/tini.asc "https://github.com/krallin/tini/releases/download/v$TINI_VERSION/tini-$dpkgArch.asc" \
@@ -44,7 +49,7 @@ RUN apt-get update \
                   $buildDeps \
                   '*-dev' \
  && rm -rf /var/lib/apt/lists/* \
- && rm -rf /tmp/* /var/tmp/* /usr/lib/ruby/gems/*/cache/*.gem /usr/lib/ruby/gems/3.*/gems/fluentd-*/test
+ && rm -rf /tmp/* /var/tmp/*
 
 RUN groupadd -r fluent && useradd -r -g fluent fluent \
     # for log storage (maybe shared with host)