An actuator allows miniaturization by realizing back-and-forth rotating motion of, for example, an electric brush without a drive transmitting mechanism which is a separate entity from a drive source. In a movable body (110) of this actuator (100), an outer yoke (150) is provided with sidewalls (152 and 153) located opposing each other spaced a predetermined interval apart. A magnet (160) is provided in the outer yoke (150) through a non-magnetic body (170) and has different magnetic poles located opposing to the opposing inner wall planes of the outer yoke (150) through the air gaps. The movable body (110) is provided with a shaft (180). The fixed body (120) has a coil (128) which is located in the air gaps and which circles the magnet (160). The fixed body (120) movably supports the movable body (110) through elastic bodies (130). An alternating current supplying section (140) supplies to the coil (128) the alternating current of a frequency virtually equal to the resonance frequency of the movable body (110).