diff --git a/lib/rggen/core/builder/builder.rb b/lib/rggen/core/builder/builder.rb
index c2214fa..9eec153 100644
--- a/lib/rggen/core/builder/builder.rb
+++ b/lib/rggen/core/builder/builder.rb
@@ -95,6 +95,7 @@ def register_input_components
         def_delegator :plugin_manager, :load_plugin
         def_delegator :plugin_manager, :load_plugins
         def_delegator :plugin_manager, :setup_plugin
+        def_delegator :plugin_manager, :update_plugin
 
         private
 
diff --git a/lib/rggen/core/builder/plugin_manager.rb b/lib/rggen/core/builder/plugin_manager.rb
index 7df2cc5..aaa30a6 100644
--- a/lib/rggen/core/builder/plugin_manager.rb
+++ b/lib/rggen/core/builder/plugin_manager.rb
@@ -77,13 +77,20 @@ def setup_plugin(plugin_name, &)
           @plugins << PluginSpec.new(plugin_name, &)
         end
 
+        def update_plugin(plugin_name)
+          plugin =
+            find_plugin(plugin_name) ||
+            (raise PluginError.new("unknown plugin: #{plugin_name}"))
+          block_given? && yield(plugin)
+        end
+
         def activate_plugins
           do_normal_activation
           do_addtional_activation
         end
 
         def activate_plugin_by_name(plugin_name)
-          @plugins.find { |plugin| plugin.name == plugin_name }
+          find_plugin(plugin_name)
             &.then do |plugin|
               plugin.activate(@builder)
               plugin.activate_additionally(@builder)
@@ -103,6 +110,10 @@ def read_plugin_file(info)
           raise Core::PluginError.new("cannot load such plugin: #{info}")
         end
 
+        def find_plugin(plugin_name)
+          @plugins.find { |plugin| plugin.name == plugin_name }
+        end
+
         def activate_plugin_gem(info)
           if (gemspec = find_gemspec(info))
             gem gemspec.name, gemspec.version
diff --git a/lib/rggen/core/dsl.rb b/lib/rggen/core/dsl.rb
index e01c1f3..05aa8cc 100644
--- a/lib/rggen/core/dsl.rb
+++ b/lib/rggen/core/dsl.rb
@@ -26,7 +26,8 @@ module DSL
         :enable,
         :enable_all,
         :delete,
-        :setup_plugin
+        :setup_plugin,
+        :update_plugin,
       ].each do |method_name|
         def_delegator :'RgGen.builder', method_name
       end
diff --git a/spec/rggen/core/builder/plugin_manager_spec.rb b/spec/rggen/core/builder/plugin_manager_spec.rb
index 26d0282..74f921a 100644
--- a/spec/rggen/core/builder/plugin_manager_spec.rb
+++ b/spec/rggen/core/builder/plugin_manager_spec.rb
@@ -266,4 +266,22 @@ def setup_plugin_expectation(**args)
       end
     end
   end
+
+  describe '#update_plugin' do
+    it '指定されたプラグインを更新する' do
+      plugin = nil
+      plugin_manager.setup_plugin(:foo) { plugin = _1 }
+
+      expect { |b| plugin_manager.update_plugin(:foo, &b) }
+        .to yield_with_args(equal(plugin))
+    end
+
+    context '指定されたプラグインが未定義の場合' do
+      it 'PluginErrorを起こす' do
+        plugin_manager.setup_plugin(:foo) {}
+        expect { plugin_manager.update_plugin(:bar) }
+          .to raise_rggen_error RgGen::Core::PluginError, 'unknown plugin: bar'
+      end
+    end
+  end
 end
diff --git a/spec/rggen/core/builder/plugin_spec_spec.rb b/spec/rggen/core/builder/plugin_spec_spec.rb
index 52dbd97..f9bd113 100644
--- a/spec/rggen/core/builder/plugin_spec_spec.rb
+++ b/spec/rggen/core/builder/plugin_spec_spec.rb
@@ -1,10 +1,6 @@
 # frozen_string_literal: true
 
 RSpec.describe RgGen::Core::Builder::PluginSpec do
-  let(:plugin_spec) do
-    described_class.new(plugin_name, plugin_module)
-  end
-
   let(:plugin_name) do
     :foo
   end