An interchangeable lens is disclosed which prevents the camera body and interchangeable lens from being damaged even if an attempt is made to erroneously mount therebetween. The interchangeable lens is a second interchangeable lens whose flange back is the same as that of a first interchangeable lens and includes a protruding portion protruding from a mount reference surface. The protruding amount of the protruding portion is set when the second interchangeable lens has a specific phase relationship with a first camera, so that the protruding portion contacts a first wall portion of the first camera, and is set when the second interchangeable lens has a phase relationship with the first camera other than the specific phase relationship and a bayonet lug of the second interchangeable lens contacts a bayonet lug of the first camera, so that the protruding portion is away from the first wall portion.