To simplify the step of forming a resin layer on the surface of a base material and stabilize the quality of the resin layer.

Firstly, the base material 11 is fixed in a cavity 24 so as to generate a gap S corresponding to the thickness of the resin layer 12 between the inner face of the cavity 24 of a molding die 20 and the surface of the base material 11. In the second place, a resin material is flowed into the gap S through an opening part 28. Thereafter, the resin layer 12 is formed on the surface of the base material 11 by curing or hardening the resin material and released from the molding die, which result in manufacturing a resin decorative board 10 provided with the resin layer 12 on the surface of the base material 11.