To provide a resin part enhanced in the appearance quality of the parting part of its skin layer and reduced in impingement sound without altering a mold structure.

In a method for manufacturing the resin part wherein the boundary part of a skin and a base material is exposed on a design surface, the skin 2 is arranged in a mold and, when the base material integrated with the rear surface of the skin 2 is formed by injection molding, an elastic projected part 22 is formed on the rear surface of the skin in the vicinity of the boundary line 12 so as to be projected on the rear surface side of the skin to come into contact with the other molding surface of the mold and injection molding is performed in such a state that the elastic projected part 22 is compressed by the mold. Since the skin 2 is brought into contact with the molding surface of the mold under pressure by the elastic projected part 22 to be sealed, the leak of a resin is prevented.