The device has motor housing side annular engagement portion 40 formed at outer circumferential surface of end surface portion of motor housing 11 which is opposite side to output shaft portion of rotation shaft of electric motor; and metal cover side annular engagement portion 38 formed at opening end 37 of metal cover 12 that covers electronic control unit and engaged with motor housing side annular engagement portion 40. Fixing region is formed by fixing metal cover side annular engagement portion 38 to motor housing side annular engagement portion 40 in a fixing manner without using any fixing screw in a state in which metal cover side annular engagement portion 38 is engaged with motor housing side annular engagement portion 40. Sealing region is formed between fixing region and opening end 37 of the metal cover 12 with liquid sealant 41 applied between fixing region and opening end 37.