A light shielding structure in an optical apparatus includes first and second relatively-movable members, each having an engaging portion engaged with each other and relatively movable to each other so as to change an amount of mutually overlapping area therebetween; and a light shielding member provided between the engaging portions. The light shielding member is elastically deformed into a light shielding shape in which the light shielding member inwardly bends toward an optical axis of the optical apparatus to protrude from the engaging portions due to the mutually overlapping area between the engaging portions decreasing, and the light shielding member is elastically deformed into a retracted shape in which the light shielding member is housed between opposing surfaces of the engaging portions due to the mutually overlapping area between the engaging portions increasing, in accordance with a relative movement between the engaging portions.