A method is provided that enables the formation of multiple level plated products with large plating depth. A negative photoresist composition comprising (a) an alkali-soluble resin, (b) an acid generator, and (c) other components is used, and a plated product is formed by (A) a step of forming a layer of this negative photoresist composition, and then either heating or not heating, before conducting exposure; (B) a step of repeating the step (A) so that the step is performed a total of 2 or more times, thereby superimposing layers of the negative photoresist, and subsequently developing all of these layers simultaneously to form a multilayer resist pattern; and (C) a step of conducting plating treatment within this multilayer resist pattern.