PURPOSE: To shorten a manufacturing process, by joining films, on the surface of which a membrane is formed, to each other.

CONSTITUTION: A film 5 made of transparent thermoplastic synthetic resin, on the surface of which a cured membrane layer 5b is formed, is molded into a form similar to a nonflat surface form of a molded product main body 4a with vacuum molding. Then mold clamping is performed by setting up the film 5 molded in this manner in the direction facing on a mold surface in a cavity part 11 of an injection mold so that the cavity 11 is formed between a base 5a surface of the film 5 and the other side mold surface. Then liquid synthetic resin, which is heated and molten, is filled into the cavity 11 by injecting the same into the cavity 11, the film 5 having the cured membrane layer 5b is unified with the surface of the molded product main body 4a through lamination along with molding of the molded product main body 4a and resin molded product is manufactured.