uninitialized constant UserController

Rails 3.1.3

I am trying to create an administrator page. 'User' table has a field,
admin:boolean, then user having 'admin=true' can only access it, as you
can imagine.

But accessing

http://localhost:3000/admin/user

gives an error,

   uninitialized constant UserController

I have 'controllers/admin/admin_application_controller.rb'

class Admin::AdminApplicationController < ApplicationController
  before_filter :admin_login_required

  def admin_login_required
    if @current_user.admin
      return true
    end
    redirect_to :controller => "/"
    return false
  end
end

also, 'controllers/admin/user_controller.rb'

class Admin::UserController < Admin::AdminApplicationController
  active_scaffold :user
end

I am guessing that the problem is routes.rb, which is

Takibou::Application.routes.draw do
  devise_for :users
  resources :projects
  root :to => 'projects#index'
  match ':controller(/:action(/:id))(.:format)'

  scope 'admin' do #HERE!!!!!
    resources :user
  end
end

Could anyone help me for the error?

soichi