To simplify the structure of an electrical contact on the lens unit side, and to obtain a sufficient speed at which the process of communicating with the camera body side is performed.

A lens unit 4 includes a lens barrel 6 and a lens-side mounting section 8. The lens-side mounting section 8 has: a mount main body 33; a pawl member 34; a mounting substrate 35; and a pressing plate 36. The projecting parts 41a to c of the mount main body 33 and the parts 49a to c of the pawl member 34 compose a bayonet pawl. The mounting substrate 35 is fitted in the back face of the pawl member 34. Connection contacts are mounted on one of the mounting faces of the mounting substrate 35 where as a CCD 25 is mounted on the other face 35b of it. When the lens unit 4 is attached to the camera body, the connection contacts mounted on the mounting substrate 35 come into contact with connection terminals on the camera body side.