An electroplating device including an anode inserted through and disposed in a hole provided in a work and communicating with the outside, and a member for rotating the work about its center axis and supplying a plating electric current to the work. Alternatively, a separate member may supply the plating electric current to the work. A plating solution in the hole in the work may be allowed to flow. Thus, a uniform plated film can be formed on both of the outer and inner surfaces of the work having the communicating with the outside such as a ring-shaped work, of which a ring-shaped bonded magnet is representative, by using the electroplating device.