PURPOSE: To monitor the trouble of a destaticizer quickly, easily and exactly, by monitoring the operating condition of the destaticizer by detecting an electric potential of a nonimage part of a photoreceptor after destaticization.

CONSTITUTION: A nonimgae part of a photosensitive drum 1 charged uniformly by a charging device 2 is destaticized by a destaticizer 3 to become zero potential. The zero potential is detected by a sensor 10 provided between the device 2 and a developing device 5 and the presence or absence of the fault of the destaticizer etc. is monitored quickly, easily and exactly. The same monitor is also performed by connecting a breaking display means with each of many luminous body groups for destaticization and by comparing the toner consumption amount at a developing device with the reference value.