A photosensitive film, which has a transparent support and a silver salt emulsion layer containing a silver salt formed thereon, is exposed and developed to form a metallic silver portion. The base material to be plated is electrified in an electrolytic solution free of plating substances, using the metallic silver portion as a cathode. Then, the electrified base material is subjected to an electroless plating treatment to form a first plated layer only on the metallic silver portion. The base material is subjected to an electroplating treatment to form a second plated layer on the first plated layer, further form a third plated layer on the second plated layer.