A power semiconductor module includes a plurality of sets of semiconductor switching elements, a molded resin casing containing the semiconductor switching elements, screw holders for receiving mounting screws formed at bottom regions of four corners of the molded resin casing, first terminal blocks having main circuit terminals, and arranged on a central region of a top surface of the molded resin casing, and second terminal blocks having control terminals arranged at a side edge of the molded resin casing apart. Insulating separation walls having a configuration of a rib erect from a surface of the second terminal blocks, and are interposed between groups of the control terminals corresponding to the sets of semiconductor switching elements, and between the screw holder including the mounting screw therein on the molded resin casing and the control terminal at a high voltage side adjacent to the screw holder.