A dimmer includes a pair of pivoting sections provided across an optical axis of a light beam and having pivot axes and a pair of light blocking sections held by the pair of pivoting sections and configured to pivot following pivoting of the pivoting sections to block the light beam. In a maximum light blocking state, positions in the optical axis direction of opposed ends on the optical axis side of the pair of light blocking sections are different from each other. In the maximum light blocking state, the opposed ends on the optical axis side of the pair of light blocking sections are arranged to overlap each other in a direction along the optical axis.