A rotor is constituted by a two-pole permanent magnet, and enabled to rotate by a predetermined angle in a direction corresponding to the direction electric current supplied to a stator coil. Two shutter blades are moved by a driving pin which is integrally provided with the rotor, to perform opening and closing operations. A fully opened state and a closed state, which are obtained by such operations, are maintained by an attractive force, which is obtained from a magnetic force of the rotor and acts between the rotor and each of four iron pins, even when the stator coil is not energized. Further, an exposure aperture regulating position established by a closing operation of the two shutter blades is beyond a midpoint position corresponding to an intermediate state from the fully opened state to the closed state. Moreover, an exposure aperture regulating state is maintained by the attractive force, which acts during a non-energized state the stator coil so as to cause the shutter blades to close, and the urging force of a spring.