An image forming apparatus includes an image forming device, a time detection unit, a humidity measurement unit and a controller. The image forming device includes a photoconductive body, a developing device and a transfer device. The time detection unit detects information concerning a stop time period of the developing device. The humidity measurement unit is provided in a casing in which the image forming device is provided and measures a humidity. The controller controls a developer supply member in the developing device based on the information concerning the stop time period detected by the time detection unit and information concerning the humidity measured by the humidity measurement unit, so as to rotate at a lower speed than a rotation speed at a normal time before the developing device starts a first developing operation after the developing device stopped.