diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 6b60559..e6a7d5c 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -19,7 +19,6 @@ jobs:
           - 2.6
           - 2.7
         gemfile:
-          - rails42.gemfile
           - rails50.gemfile
           - rails51.gemfile
           - rails52.gemfile
@@ -34,8 +33,6 @@ jobs:
             gemfile: rails60.gemfile
           - ruby: 2.5
             gemfile: rails61.gemfile
-          - ruby: 2.7
-            gemfile: rails42.gemfile
 
     env:
       CI: true
diff --git a/Appraisals b/Appraisals
index cdd7d65..03e50b3 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,40 +1,18 @@
-appraise 'rails32' do
-  gem 'activerecord', '~> 3.2.0'
+appraise 'rails50' do
+  gem 'activerecord', '~> 5.0.0'
   gem 'sqlite3', '< 1.4'
 end
 
-appraise 'rails40' do
-  gem 'activerecord', '~> 4.0.0'
+appraise 'rails51' do
+  gem 'activerecord', '~> 5.1.0'
   gem 'sqlite3', '< 1.4'
 end
 
-appraise 'rails41' do
-  gem 'activerecord', '~> 4.1.0'
+appraise 'rails52' do
+  gem 'activerecord', '~> 5.2.0'
   gem 'sqlite3', '< 1.4'
 end
 
-appraise 'rails42' do
-  gem 'activerecord', '~> 4.2.0'
-  gem 'sqlite3', '< 1.4'
-end
-
-if RUBY_VERSION >= '2.2.2'
-  appraise 'rails50' do
-    gem 'activerecord', '~> 5.0.0'
-    gem 'sqlite3', '< 1.4'
-  end
-
-  appraise 'rails51' do
-    gem 'activerecord', '~> 5.1.0'
-    gem 'sqlite3', '< 1.4'
-  end
-
-  appraise 'rails52' do
-    gem 'activerecord', '~> 5.2.0'
-    gem 'sqlite3', '< 1.4'
-  end
-end
-
 if RUBY_VERSION >= '2.6.0'
   appraise 'rails60' do
     gem 'activerecord', '~> 6.0.0'
diff --git a/README.md b/README.md
index 8cecebd..a486bbe 100644
--- a/README.md
+++ b/README.md
@@ -183,8 +183,8 @@ $ gem install jp_prefecture
 
 ## サポートしているバージョン
 
-* Ruby: 1.9.3 / 2.0 / 2.1 / 2.2 / 2.3 / 2.4 / 2.5 / 2.6 / 2.7
-* Rails: 3.2 / 4.0 / 4.1 / 4.2 / 5.0 / 5.1 / 5.2 / 6.0 / 6.1
+* Ruby: 2.4 / 2.5 / 2.6 / 2.7
+* Rails: 5.0 / 5.1 / 5.2 / 6.0 / 6.1
 
 
 ## Contributing
diff --git a/README_EN.md b/README_EN.md
index 6f960f1..3c4d236 100644
--- a/README_EN.md
+++ b/README_EN.md
@@ -184,8 +184,8 @@ $ gem install jp_prefecture
 
 ## Supports
 
-* Ruby: 1.9.3 / 2.0 / 2.1 / 2.2 / 2.3 / 2.4 / 2.5 / 2.6 / 2.7
-* Rails: 3.2 / 4.0 / 4.1 / 4.2 / 5.0 / 5.1 / 5.2 / 6.0 / 6.1
+* Ruby: 2.4 / 2.5 / 2.6 / 2.7
+* Rails: 5.0 / 5.1 / 5.2 / 6.0 / 6.1
 
 
 ## Contributing
diff --git a/gemfiles/rails32.gemfile b/gemfiles/rails32.gemfile
deleted file mode 100644
index 3fb1b39..0000000
--- a/gemfiles/rails32.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 3.2.0"
-gem "sqlite3", "< 1.4"
-
-gemspec path: "../"
diff --git a/gemfiles/rails40.gemfile b/gemfiles/rails40.gemfile
deleted file mode 100644
index e973c43..0000000
--- a/gemfiles/rails40.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.0.0"
-gem "sqlite3", "< 1.4"
-
-gemspec path: "../"
diff --git a/gemfiles/rails41.gemfile b/gemfiles/rails41.gemfile
deleted file mode 100644
index c7d1b78..0000000
--- a/gemfiles/rails41.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.1.0"
-gem "sqlite3", "< 1.4"
-
-gemspec path: "../"
diff --git a/gemfiles/rails42.gemfile b/gemfiles/rails42.gemfile
deleted file mode 100644
index 192c984..0000000
--- a/gemfiles/rails42.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.2.0"
-gem "sqlite3", "< 1.4"
-
-gemspec path: "../"
diff --git a/jp_prefecture.gemspec b/jp_prefecture.gemspec
index 0f60c14..57479ec 100644
--- a/jp_prefecture.gemspec
+++ b/jp_prefecture.gemspec
@@ -15,10 +15,11 @@ Gem::Specification.new do |gem|
   gem.name          = 'jp_prefecture'
   gem.require_paths = ['lib']
   gem.version       = JpPrefecture::VERSION
+  gem.required_ruby_version = '>= 2.4.0'
 
   gem.add_development_dependency 'rake'
   gem.add_development_dependency 'rspec'
-  gem.add_development_dependency 'activerecord', '>= 4.2.0'
+  gem.add_development_dependency 'activerecord', '>= 5.0.0'
   gem.add_development_dependency 'sqlite3'
   gem.add_development_dependency 'simplecov'
   gem.add_development_dependency 'simplecov-lcov'