PURPOSE: To reduce shock caused by closing of aperture blades, improve durability and prevent bounding by providing plural switching devices that conduct successively at the time of breaking of power source and supply aperture blade closing current and a condenser.

CONSTITUTION: When power source is cut off, power source voltage VB becomes 0. A transistor 11 conducts and charging charge of the first condenser C1 discharges let flow aperture blade closing current I to a driving coil RL through a diode D3. When discharge of the condenser C1 advances and the potential of a point (d) lowers to a specified value, a lambda diode 14 conducts, triggers SCR 13 and conducts a transistor 12. consequently, charging charge of the second condenser C2 discharges through a diode D5 and current I flows in the driving coil RL to further close aperture blades.