An in-mold coating method for molding a molded product with an excellent external appearance. A resin molded product is kept pressed against a mold cavity surface until immediately before coating. Mold-clamping force in a second step in which the shape of the resin molded product is fixed and that in a fourth step are selected so that the deformation of the mold cavity by the mold-clamping forces is substantially the same in the second and fourth steps. Even if the mold cavity deforms by the mold-clamping force in the second step, the mold cavity deforms similarly in the fourth step to provide a uniform coating thickness. Alternatively, a mold-clamping force smaller than that in the first step is selected for the second step to reduce the degree of deformation of the mold cavity and to achieve a uniform coating thickness.