In the method of manufacturing a semiconductor device that semiconductor chips are mounted facing-up on the printed wiring board on which a protective insulation film is formed by means of a film-like resist and a plurality of the semiconductor chips are collectively molded by a transfer mold technology, when transfer molding is performed, among the adsorption face of the printed wiring board and the lower die to make adsorb the printed wiring board, the through holes reaching the exterior space of the lower die from the vicinity of the end portion opposing the gate to pour mold resin of a mold cavity are formed as many as possible in order to prevent a short circuit and an open circuit by big deformation of a bonding wire connecting an electrode of the semiconductor chip and an conductor pattern of the printed wiring board.