Heat radiation base body 23 that is adjacent to electric motor unit EM and extends in direction of rotation shaft of electric motor is provided close to rotation shaft of electric motor. Board 24 of one electronic control unit of redundant system is fixed to heat radiation base body along direction in which heat radiation base body 23 extends with thermal conduction to heat radiation base body 23 allowed. Board 26 of the other electronic control unit of redundant system is fixed to heat radiation base body so as to face to board 24 of one electronic control unit of redundant system, with thermal conduction to heat radiation base body 23 allowed. Rotation position detection circuit board 22 to which neutral terminals 31 of electric motor for each phase are connected is provided between heat radiation base body 23 and motor housing 20.