To provide a light quantity controller having a compact structure, which uses an electromechanical transducer as a drive source, is easy to assemble because the number of parts is small, capable of properly rocking a light-shielding blade and of reducing the height of the controller in an optical axis direction, thereby suppressing increase in the size of the controller as a whole, the cost and the power consumption.

The light-shielding blade 20 provided in a base plate 10 is rocked by a light-shielding blade rocking means 30, to narrow a first light quantity control hole 13 by the light-shielding blade 20 and control a quantity of passing light. The light-shielding blade rocking means 30 is configured so that the base plate 10 includes: a drive member 31; a friction engagement member 32, which supports the drive member 31 in a friction-engaged state; the electromechanical transducer 33, whose one end surface in an expansion and contraction direction is fixed to the end surface of the drive member 31; a head to be driven 34, which is fixed to the other end surface of the electromechanical transducer 33; and a drive pin 35, which is provided integrally with the head to be driven 34 and connected to the light-shielding blade 20.