A light quantity adjustment apparatus has a board including an exposure aperture, blade members adjusting a quantity of light passing through the exposure aperture, and a driving device for driving the blade members. The driving device is provided with an electromagnetic coil, a magnet rotor rotating by applying a current to the electromagnetic coil, a rotating shaft, a coil frame having bearings, a reference surface for positioning formed in the coil frame, and a shield yoke supported relative to the reference surface and magnetically shielding the magnet rotor. The board includes a support plane supporting the blade members, a concave portion in the support plane to store the driving member, a support portion in the concave portion to support one end of the shield yoke, and a holding device for storing and supporting the driving member in the concave portion.