An actuator (100) includes a movable body (120) including a cylindrical magnet (123) having on a circumferential surface thereof alternating N and S pole faces along a circumferential direction thereof. An immovable body (110) includes pole teeth arranged along the circumferential direction so as to face the circumferential surface of the magnet and that are equal in number to the N pole faces, and a coil that receives an alternating current of a frequency substantially equal to a resonance frequency of the movable body to excite the pole teeth to have alternately different polarities in the circumferential direction. The movable body is held by the immovable body in a rotatable manner, and a neutral position for rotation of the movable body is a position at which center positions of the pole teeth in the circumferential direction and boundary positions between the pole faces of the magnet face each other.