PURPOSE: To execute diaphragm control for a solid-state image pickup device with simple constitution and with low power consumption.

CONSTITUTION: A torsion coil spring (pressing means) 5 is fixed to a driving arm 4 whose one end is stuck to a 1st bottom board 1 and whose other end is stuck to the rotary shaft of a galvanometer. Thus, the pressing direction of the spring 5 is a CCW direction (diaphragm opening direction), and 1st and 2n stop blades 2 and 3 slide upward and downward, respectively, so that the diaphragm becomes open. In the case of stopping down, the driving arm 4 is driven in a CW direction (diaphragm closing direction) against the pressing force of the spring by the driving means of the galvanometer, thereby accomplishing stopping down.