In a single lens reflex camera including a camera body provided with a film receptacle, a film transporting mechanism and an operating member for effecting film advancing and shutter cocking; a shutter block in which shutter blades or the like and shutter actuating and controlling mechanism are associated as a unit on a base plate; and a front plate formed with a mount for the camera objective lens and having attached thereto a mirror box which is provided with a reflex mirror, a mirror driving mechanism and a diaphragm driving mechanism, the front plate assembly to which the shutter block is coupled is attached to the camera body, whereby interconnection between the shutter mechanism, the mirror and the diaphragm mechanism is improved.