diff --git a/Gemfile b/Gemfile
index c7433116..5aa29843 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,3 +2,10 @@ source 'https://rubygems.org'
 
 # Specify your gem's dependencies in csv.gemspec
 gemspec
+
+group :development do
+  gem "bundler"
+  gem "rake"
+  gem "benchmark_driver"
+  gem "test-unit", ">= 3.4.8"
+end
diff --git a/csv.gemspec b/csv.gemspec
index 11c5b0f2..f5cf5827 100644
--- a/csv.gemspec
+++ b/csv.gemspec
@@ -55,10 +55,4 @@ Gem::Specification.new do |spec|
   spec.extra_rdoc_files = rdoc_files
 
   spec.required_ruby_version = ">= 2.5.0"
-
-  # spec.add_dependency "stringio", ">= 0.1.3"
-  spec.add_development_dependency "bundler"
-  spec.add_development_dependency "rake"
-  spec.add_development_dependency "benchmark_driver"
-  spec.add_development_dependency "test-unit", ">= 3.4.8"
 end