An object is to achieve a compact design by using a dead space in an inverter box effectively, to improve cooling properties of heat-generating electrical components disposed on a control circuit board of an inverter, and to increase flexibility of wiring layout. In an inverter box provided at a periphery of a housing, a heat-dissipating flat portion that is parallel to a control circuit board of an inverter is formed, and electrical components are disposed in a space between the heat-dissipating flat portion and the control circuit board. Preferably, the electrical components are installed so that the back faces thereof abut against the heat-dissipating flat portion either directly or via a heat-conducting member. More preferably, faces of the electrical components on the board side abut against the control circuit board.