A stator is fixed to a frame of an electric motor. A rotor is rotatably mounted to the frame to face the stator in a radial direction. A heat sink, to which a control substrate is attached, is mounted in an opening of the frame. A motor cover is attached to a front end of the frame to cover the heat sink. An adhesive groove, which has a fixed depth and is filled with an adhesive, is formed on the front end. A joining portion is formed on the rear end of the motor cover, and is inserted into the adhesive groove is an axis of rotation direction to join the motor cover with the frame in a liquid-tight manner.