A light adjusting apparatus includes substrates arranged in parallel, each including an opening to pass light, a rotary shaft member which is rotatable around an axis perpendicular to the substrates and movable in an axial direction, a light adjusting section fixed integrally to the rotary shaft member in a space between the substrates and configured to move to an insertion position or a retracted position along with the rotation of the rotary shaft member and adjust light that passes through the opening, and a holding member configured to restrict the rotation of the light adjusting section that moves to one substrate side in the space from the insertion/retracted position and allow the rotation of the light adjusting section that moves to the other substrate side in the space.