PURPOSE: To reduce the malfunction of no-toner display by repeating the cycle of operation for detecting the remaining amount of a developer more than twice after copying operation is stopped, and making the no-toner display when a no- toner state is detected continuously.

CONSTITUTION: A developing device is powered on and whether there is toner left or not is detected in a step I; when the no-toner state is not detected, a step II is entered. A timer is used to clock a specific time after a specific num ber of copies are taken and whether there is left or not is detected at (8) in the step II. When there is toner left, processed (3)W(8) are repeated again. When the no-toner state is detected, the no-toner display is not made immediately and the processed (3)W(8) in a step III are carried out; when the no-toner state is detected, again, that is displayed at the process (9). When the no-toner state is not detected, the control is returned to the beginning of the step II.