A holding apparatus includes a holding member configured to hold an optical element, the holding member having an internal space that extends in a circumferential direction and has different sectional shapes perpendicular to the circumferential direction on at least two locations, a fixing member arranged outside of the holding member and configured to fix the holding member from an outside of the holding member, and a pressing member configured to press the internal space by supplying a fluid to the internal space, and to deform the holding member.