PURPOSE: To prevent toner from sticking on a photosensitive body in a developing device when development is not carried out by energizing a guide member and allowing it to collide against a guide member colliding part provided to both breadthwise end parts of the developing device when the development is performed.

CONSTITUTION: When a 2nd developing device 26 is selected, a driving shaft 58 is driven after the developing cycle of a 1st developing device 24 or a copying cycle and a support bracket 50 is elevated by a pushing-up pin 64. The bearing 52 of a guide roll 34 moves away from the abutting part of the developing part and a guide roll 10 is moved away to the position where toner on a developing roll 30 does not stick on an electrostatic latent image. The device 24 is turned off by this operation and the device 26 is put in operation to develop the electrostatic latent image formed on a photosensitive body 10. When the electrostatic latent image on the photosensitive body 10 is developed by the device 24, the device 26 is turned off and the driving shaft 58 is reversed. Thus, the toner is prevented from sticking on the photosensitive body of the developing device when the development is not performed.