A heat radiation base body extending in a direction of a rotation shaft of an electric motor close to the rotation shaft is provided at an end surface of a motor housing accommodating the electric motor. A board of one electronic control unit of a redundant system is fixed to the heat radiation base body along the direction in which heat radiation base body extends with thermal conduction allowed. A board of the other electronic control unit of redundant system is fixed to the heat radiation base body along a direction in which the heat radiation base body extends, so as to face the board of one electronic control unit, with thermal conduction allowed. A cover covering these is fixed to an end surface of the motor housing without a bolt. Thus, a housing accommodating the electronic control unit is not necessary. A sealing part is only the connecting portion between the motor housing and cover, thereby eliminating additional structure of the sealing part, sealing component required for seal and bolt.