To enable an uneven coated layer to be formed on a crimpy surface by thermally melting a resin powder containing a foaming material partially to form a coated layer after allowing the powder to stick to the surface of a work.

Two different types of powder 1, 2 are used for forming a coated layer. One type of powder 1 is made of a single resin as a whole, and the other type 2 contains a foaming material. When forming the coated layer on the surface of a work using both different types of powder, these powders are mixed. Next, the preheated work W is soaked in this mixture, and a gas is blown up toward the work W from the lower part of a container. After causing the powders 1, 2 to stick to the work W, the work W is loaded in a heating furnace to thermally melt the powders 1, 2. Thus the constituent resins of the molten powders 1, 2 are fused to each other to form a crimped coated layer 5.