Interchangeable lens and camera system

An interchangeable lens comprising:

• a lens barrel portion configured to hold a lens group;
• a lens mount detachably coupled to a camera main body;
• and
• a spacer sandwiched between the lens barrel portion and the lens mount in an optical axis direction of the interchangeable lens,
• wherein the spacer having, in a circumferential direction of the interchangeable lens, a plurality of first seat surfaces protruding in the optical axis direction, respectively, at one surface thereof with respect to the optical axis direction, and having, in the circumferential direction, a plurality of second seat surfaces protruding in the optical axis direction, respectively, at the other surface thereof with respect to the optical axis direction, and
• one plurality of seat surfaces of the plurality of first seat surfaces and the plurality of second seat surfaces are disposed with different heights in the optical axis direction such that a surface defined by the plurality of second seat surfaces has an angle with respect to a surface defined by the plurality of first seat surfaces.