An IGBT serving as a heat-generating electrical component mounted on the lower surface of a lower board serving as a control circuit board of an inverter is disposed in abutment with a heat-dissipating flat section provided on an inner wall of an inverter box provided on the outer periphery of a housing so that the heat of the IGBT is dissipated toward the housing. Moreover, a spacer member is interposed between the lower board and the IGBT so as to fill a space between the lower board and the IGBT, and the spacer member is rigid enough that the lower board and the IGBT are prevented from being displaced toward and away from each other.