An actuator includes a motor including a first rotor rotatable in a circumferential direction about a center axis extending in a vertical direction, a second rotor including a sensor magnet and rotatable in the circumferential direction about the center axis, and a speed reducer that reduces rotation of the first rotor and transmits a torque to the second rotor. The motor includes a stationary portion including a stator facing the first rotor and a first bearing rotatably supporting the first rotor with respect to the stationary portion. The stationary portion includes a sensor which faces a portion of a trajectory of the sensor magnet rotating in the circumferential direction and detects a rotation position of the sensor magnet.