An interchangeable lens (second interchangeable lens) is disclosed which allows a protruding amount from a mount reference surface of the interchangeable lens to be increased. The second interchangeable lens has a protruding portion protruding from a mount reference surface toward an image plane, has a larger protruding amount than the first interchangeable lens and has the same flange back as the first interchangeable lens. The first camera prevents mounting of the second interchangeable lens by the protruding portion of the second interchangeable lens contacting the first wall portion. The second camera includes a second wall portion provided at a position retreated from the protruding portion. The second camera includes a rotatable mirror member, and the rotation center of the mirror member is positioned on the opposite side of a finder optical system with respect to a plane including an in-plane direction of the mirror member.