A prime mover includes a stator fixed to a housing and a rotor relatively rotatable relative to the stator. The prime mover outputs torque from the rotor by being supplied with electric power. A speed reducer reduces the torque of the prime mover and outputs the reduced torque. One bearing portion rotatably supports the rotor. The speed reducer includes an input portion that is coaxial and integrally rotatable with the rotor and receives the torque from the rotor.