A power semiconductor device includes a conductive insertion member as an external terminal projecting from a surface of the power semiconductor device facing a printed wiring board. The printed wiring board includes a conductive fitting member mounted on a pad part of the printed wiring board. The fitting member receives the insertion member therein when the power semiconductor device is connected to the printed wiring board. The insertion member has a recessed portion formed on a side surface of the insertion member. The fitting member has a projecting portion with elasticity formed on an inner side surface of the fitting member. The elasticity causes the projecting portion of the fitting member to contact the recessed portion of the insertion member under pressure when the insertion member is inserted into the fitting member.