A device for preventing erroneous handling of a camera capable of dual type automatic exposure control including shutter time preference and diaphragm preference, wherein the device senses whether the camera is set at a diaphragm preference position or at a diaphragm automatic adjusting position with regard to the diaphragm setting means, and whether the shutter time preference position or the shutter time automatic adjusting position is selected for the shutter time setting means. The camera is rendered inoperative when both the diaphragm setting means and the shutter time setting means are set in their respective preference positions.