A coating structure is provided with a metal-made substrate (1), an undercoating (2) provided on the substrate, and an insulating film (3) provided on the undercoating. The insulating film has a plurality of films (31, 32) comprising mutually different materials, and the plurality of films are layered in alternating fashion. The undercoating is formed by a method other than a coating method which uses a surface chemical reaction occurring on the substrate, and the portion of the undercoating in contact with the substrate is amorphous. Through this configuration, even when foreign matter adheres to the substrate, the foreign matter can be covered by the undercoating. Providing the insulating film on the undercoating makes it possible to inhibit foreign matter from causing defects in the formation of the insulating film.