diff --git a/lib/dekiru.rb b/lib/dekiru.rb
index ce7c16c..e718de4 100644
--- a/lib/dekiru.rb
+++ b/lib/dekiru.rb
@@ -1,7 +1,6 @@
 require 'dekiru/version'
 require 'dekiru/railtie' if defined?(::Rails)
 require 'dekiru/helper'
-require 'dekiru/validators/existence'
 require 'dekiru/data_migration_operator'
 require 'dekiru/mail_security_interceptor'
 require 'dekiru/camelize_hash'
diff --git a/lib/dekiru/validators/existence.rb b/lib/dekiru/validators/existence.rb
deleted file mode 100644
index 9435f66..0000000
--- a/lib/dekiru/validators/existence.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-#   class Post < ActiveRecord::Base
-#     belongs_to :company
-#     belongs_to :user
-#     validates :user_id, presence: true, existence: { in: -> { company.users } }
-#   end
-
-module ActiveModel
-  module Validations
-    class ExistenceValidator < EachValidator
-      def validate_each(record, attribute, value)
-        ActiveSupport::Deprecation.warn('`ExistenceValidator` is deprecated and will be removed in v0.5. Please use `inclusion: { in: xx }` instead.')
-
-        unless exists?(record, value)
-          record.errors.add(attribute, :existence, **options.except(:in).merge!(value: value))
-        end
-      end
-
-      def exists?(record, value)
-        unless options[:in].respond_to?(:call)
-          raise ArgumentError, '`in` option should be proc'
-        end
-        collection = record.instance_exec(&options[:in])
-        collection.exists?(value)
-      end
-    end
-  end
-end
diff --git a/spec/dekiru/validators/existence_spec.rb b/spec/dekiru/validators/existence_spec.rb
deleted file mode 100644
index d94730b..0000000
--- a/spec/dekiru/validators/existence_spec.rb
+++ /dev/null
@@ -1,51 +0,0 @@
-require 'spec_helper'
-
-describe ActiveModel::Validations::ExistenceValidator do
-  let(:user_class) do
-    Class.new do
-      def self.exists?(id)
-        %w[valid_id].member?(id)
-      end
-    end
-  end
-  let(:model_class) do
-    _options = options
-
-    Struct.new(:user_id, :users) do
-      include ActiveModel::Validations
-
-      def self.name
-        'DummyModel'
-      end
-
-      validates :user_id, existence: _options
-    end
-  end
-
-  describe 'validate' do
-    subject(:valid?) do
-      model_class.new(user_id, user_class).valid?
-    end
-
-    context 'with exists id' do
-      let(:user_id) { 'valid_id' }
-      let(:options) { { in: -> { users } } }
-
-      it { is_expected.to eq true }
-    end
-
-    context 'with exists not id' do
-      let(:user_id) { 'invalid_id' }
-      let(:options) { { in: -> { users } } }
-
-      it { is_expected.to eq false }
-    end
-
-    context 'with invalid option' do
-      let(:user_id) { 'valid_id' }
-      let(:options) { { in: user_class } }
-
-      it { expect { valid? }.to raise_error(ArgumentError) }
-    end
-  end
-end