PURPOSE: To readily coat a molded synthetic resin article, by preparing a coating solution consisting of one reactant capable of forming a thermosetting synthetic resin and a catalyst and a coating solution containing the other reactant, separately coating the coating solutions, reacting and curing the resultant resin.

CONSTITUTION: For example, coating on the surface of a molded sheet molding compound (SMC) synthetic resin article is completed by using a two-pack type reactive urethane coating material consisting of a polyester polyol as a principal agent and hexamethylene diisocyanate polymer as a curing agent using dibutyltin laurate as a catalyst. In the process, the SMC surface is initially coated with the first solution of the curing agent and catalyst and the resultant first film is then coated with the second solution of the principal agent and curing agent and then the third coating solution of the principal agent and curing agent is coated thereon. Baking is then carried out to complete the coating. Furthermore, the amount of the catalyst is preferably ≤0.5wt%.