To provide an actuator which is capable of outputting a large drive electromagnetic force even if an electromotive force is small.

The actuator is configured in a manner that a current is made to flow through an exciting coil 11, a magnetic circuit composed of a stator 1 and a moving member 2 is excited to generate magnetic flux, and a moving member is rectilinearly moved by the generated electromagnetic force. Movable magnetic members 21a and 21b are provided which are located between the stator 1 and the moving member 2 to form an initial gap which is smaller than an initial gap between the stator 1 and the moving member 2 between the stator 1 and the movable magnetic member itself or the moving member 2 and the movable magnetic member itself.