Mount device

A mount device for an interchangeable lens having a bayonet type mount member capable, upon rotation relative to a mount member on a camera body, of coupling with or decoupling from the latter, and a plurality of electrical connection terminals arranged, upon completion of a coupling operation of both mount members, to contact with the equal number of electrical connection terminals on the camera body so that communication become possible between the lens and the camera body. The axial rear ends of the terminals on the lens project outwardly from the rear end surface of the mount member on the lens and the rear end surface of the rearmost lens.