Disclosed is an actuator that generates the reciprocating rotational motion of an electric toothbrush or similar without employing a drive transmission mechanism as a separate entity from a drive source. An actuator (100) includes a fixed body (110) comprising an outer yoke (140) having inner wall planes that respectively oppose the magnetic pole planes of unlike poles of a magnet (150) with a predetermined gap therebetween. A coil (122) is arranged to encircle the magnet (150) between the magnetic pole planes of the unlike poles of the magnet (150) and the inner wall planes of the outer yoke (140) that respectively oppose the magnetic pole planes of the unlike poles, and this coil (122) is movably supported as a movable body (120) by way of an elastic member (130) fastened to the fixed body (110). The reciprocating rotational motion of the movable body (120) is afforded by the supply of an alternating current of a frequency approximately equivalent to the resonant frequency of the movable body (120) from an alternating current supply (180) to the coil (122).