PURPOSE: To detect surely the separating condition of a developing roll, pressing roll and developing soln. feed roll by controlling the speed of a means for driving a copying machine at a prescribed speed irrespectively of the set printing speed for the copying machine in the stage of stopping the machine.

CONSTITUTION: A switch 86 is turned off and a switch 80 is turned off when the operator pushes a switch 98. The prescribed voltage divided by resistors 82, 84 is therefore impressed to the + terminal of a comparator 90 and a driving motor 96 runs at a prescribed rotating speed irrespectively of the position of a slider of a potentiometer 88 so that a cam shaft 34 rotates at a preset rotating speed. The power source of the copying machine is turned off when a microswitch 32 turns off upon rotation of the shaft 34. The rotating speed of the motor 96 when the switch 80 turns on is thereupon controlled to the prescribed speed optimum for detecting the sepn. of a developing roll, pressing roll and developing soln. feed roll, by which the sepn. condition of the three rolls is surely detected.