A power module having three unit power modules and a control circuit board including a gate drive circuit are set up side by side and mounted on a heat exchanger. A pair of positive and negative direct current terminals for connecting the smoothing capacitor and a plurality of alternating current terminals for inputting and outputting polyphase alternating current are integrally-molded into a power module case of the power module. A plurality of control pins for providing switching devices mounted on the unit power modules with control signals are set up on the opposite side of the side where the direct current terminals and the alternating current terminals are set up, which is figured as located in the right of the drawing. The control pins of the switching devices of the unit power modules and the gate signal output terminals of the control circuit board are wire-bonded. The smoothing capacitor is mounted on the side or top of the power module.