An actuator comprising: a movable body that includes a cylindrical magnet portion having on an inner circumferential surface thereof alternating N pole faces and S pole faces along a circumferential direction thereof; an immovable body that includes an outer circumferential surface facing the inner circumferential surface of the magnet portion , pole tooth faces arranged on the outer circumferential surface along the circumferential direction, and a coil that excites the pole tooth faces ; and a torsion coil spring configured to support the movable body to the immovable body such that the movable body can produce a reciprocally rotary motion with respect to a rotary shaft which is a part of the movable body and to bias the movable body to a neutral position for the reciprocally rotary motion, wherein the coil is configured to receive an alternating current of a frequency substantially equal to a resonance frequency of the movable body , the resonance frequency being determined by an inertia of the movable body and a spring constant in a torsion direction of the torsion coil spring , and to excite the pole tooth faces to have alternately different polarities in the circumferential direction, and wherein one end of the torsion coil spring is fixed to one end of the rotary shaft of the movable body , the other end of the torsion coil spring is fixed to the immovable body , and the torsion coil spring is placed such that a central axis of the torsion direction coincides a center of the rotary shaft , and is configured to support the movable body to the immovable body such that the movable body vibrates at the resonance frequency of the movable body . a movable body that includes a cylindrical magnet portion having on an inner circumferential surface thereof alternating N pole faces and S pole faces along a circumferential direction thereof; an immovable body that includes an outer circumferential surface facing the inner circumferential surface of the magnet portion , pole tooth faces arranged on the outer circumferential surface along the circumferential direction, and a coil that excites the pole tooth faces ; and a torsion coil spring configured to support the movable body to the immovable body such that the movable body can produce a reciprocally rotary motion with respect to a rotary shaft which is a part of the movable body and to bias the movable body to a neutral position for the reciprocally rotary motion, wherein the coil is configured to receive an alternating current of a frequency substantially equal to a resonance frequency of the movable body , the resonance frequency being determined by an inertia of the movable body and a spring constant in a torsion direction of the torsion coil spring , and to excite the pole tooth faces to have alternately different polarities in the circumferential direction, and wherein one end of the torsion coil spring is fixed to one end of the rotary shaft of the movable body , the other end of the torsion coil spring is fixed to the immovable body , and the torsion coil spring is placed such that a central axis of the torsion direction coincides a center of the rotary shaft , and is configured to support the movable body to the immovable body such that the movable body vibrates at the resonance frequency of the movable body . <EOS>