To provide a light quantity controller which includes a small number of parts, is easily assembled, satisfactorily rocks a light shielding blade, is made low in height in an optical axis direction, and improves efficiency of an electromechanical conversion element.

The light shielding blade 20 provided to a base late 10 is rocked by a light shielding blade rocking means 30 so as to control the quantity of diaphragm passing light through a first aperture 13 by the light shielding blade 20. The light shielding blade rocking means 30 includes: a driving member 31 whose axial line is formed in circular-arc shape with the center of rotation of the light shielding blade 20 as the center of curvature on a plane along the base plate 10; a frictional engaging member 32 which supports the driving member 31 to be circular-arc shape in a frictional engaging state; the electromechanical conversion element 33 whose one end face is stuck to the end face of the driving member 31; a head to be driven 34 which is stuck to the other end face of the electromechanical conversion element 33; and a driving pin 35 which is provided integrally with the head to be driven 34 and coupled to the light shielding blade 20, on the base plate 10.