In a shutter-time-preference single lens reflex camera, in which the shutter time control is done with a predetermined shutter time, and diaphragm value is determined by an output information of a photometric means which measures a transmission light of a photographing lens and the above predetermined shutter time information, a camera actuating means provided in the camera body is put into operation through a magnet means provided in the camera body so that the aperture of the photographing is controlled in accordance with the above predetermined diaphragm value, and then the shutter time control is performed. Further, the camera includes an electric driving device and the driving of the electric driving device is controlled by a safety switch which, in turn, is controlled for its ON and OFF conditions by the completion of the exposure operations such as the operation of the shutter rear screen.