Conventionally, in the coating of an automobile body, midcoat coating, baking, overcoat base coating, overcoat clear coating and baking are sequentially performed on a coated product on which electrodeposition coating serving as an undercoat and baking are performed. In other words, since a total of three rounds of baking are needed, a reduction in the number of times baking is performed has been required in terms of reducing the amount of CO2 discharged and saving energy.
Hence, a coating method has been proposed in which, in the coating of an automobile body, baking is not performed after midcoat coating, wet-on-wet overcoat coating is performed, and a midcoat coating film and an overcoat coating film are baked and cured simultaneously (see, for example, Patent Document 1). This coating method is a so-called 3-coat 2-bake (hereinafter referred to as “3C2B”) coating method in which a total of three rounds of coating (undercoat, midcoat and overcoat) and a total of two rounds of baking are performed.    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2005-177631