An object of the present invention is to provide a novel method for forming an electrolytic copper plating film having excellent adhesion on the surface of a rare earth metal-based permanent magnet. The method of the present invention as a means for achieving the object is characterized in that after a magnet is immersed in a plating solution, a cathode current density of 0.05 A/dm2 to 4.0 A/dm2 for performing an electrolytic copper plating treatment is applied thereto over 10 seconds to 180 seconds to start the treatment.