PURPOSE: To form a coating of perfect form on the surface of an injection- molded product, by a method wherein a two-layer film cut into an appropriate form is mounted on an injection mold so that a silane coating becomes the outer most surface and injection molding is performed in this state.

CONSTITUTION: A silane coating displaying adhesion force strongly by applying the same to polycarbonate and baking the same is applied to a side of a polycarbonate film to a thickness of 2W10μ and the film is cut off into an appropriate form after an uncure or cure of the coating. The same is mounted on one side or both sides of a cavity part of an injection mold so that the polycarbonate film is joined unitarily to the surface of a molten material and a silane coating becomes the outermost surface. Then the film and molding material are unified within an injection mold by injecting thermoplastic resin. Then a molded product is postcured through heat treatment after injection molding, in the product whose coating is uncured.