PURPOSE: To lessen a unit in size by a method wherein a yoke forming a magnetic circuit is formed in one piece together with the base plate of a unit possessed of a magnetic circuit, or a part of the base plate is made to serve as the yoke which forms a magnetic circuit.

CONSTITUTION: When a current is made to flow through a coil 4 to produce a magnetic pole on the end surface of an upper yoke 3 which confronts a magnet 5, a magnet 5, a drive shaft 6, and a pin 7 are revolved in the direction of an arrow A around a rotation axis B as a center. With the rotation of the pin 7, a ring 8 and drive pin 9 are revolved in the direction of an arrow around the rotation axis B as a center. With the rotation of the drive pin 9, a shutter vane 11 is turned around a rotating shaft 12 of an upper base plate 10 as a center and opened. After a certain time elapses, when a reverse current is made to flow through the coil 4, the magnet 5, the drive shaft 6, and the pin 7 are rotated in an opposite direction to close the shutter vane 11. By this setup, a unit can be lessened in size, which is conducive to the miniaturization of a camera or a video.