A control part 33 rotates a developer roller 21a at a second rotation speed, which is slower than a normal rotation speed during an image formation period (first rotation speed), during a non-image formation period while a heater 14 is in use. This prevents deformation of the developer roller 21a caused by radiant heat from a photoconductive drum 41, effectively prevents the appearance of image fogging, concentration unevenness, and the like, and also suppresses toner deterioration in a development unit 21.