A camera body includes a housing, an imaging element and a body mount. The body mount is fixed to the housing, and has a portion to which an adapter can be mounted. The body mount is disposed at a position away from the light receiving face of the imaging element by the amount of a flange back. A lens back of an interchangeable lens unit is longer than the flange back. The flange back is shorter than the length obtained by subtracting the adapter length, which is the length of the adapter in the optical axis direction, from the lens back.