A transfer mold type power module ("TPM") is provided with a projection at each of the four corners on its front main surface. The TPM is also provided a first screw hole at its center. A shielding plate is provided with a second crew hole in a position that corresponds to the first screw hole. A control substrate is provided with third screw holes in positions that correspond to the projections. The shielding plate and the TPM are joined by putting a first screw through the first and second screw holes and temporarily fastening the tip of the first screw by a temporary fastening member at the rear main surface of the TPM. The control substrate and the TPM are joined by second screws via the third screw holes.