An image forming apparatus which allows a user to freely select a desired image quality is provided. The control unit 60 sets a of registration set value A1 for determining a color registration error suppression level and a dropout set value A2 for determining a dropout occurrence suppression level. Also, the control unit 60 sets a differential circumferential speed which is the difference between the circumferential speed of photoreceptor drums 1Y to 1K and the circumferential speed of an intermediate transfer belt 6 on the basis of the color registration set value A1 and the dropout set value A2. Then, the control unit 60 controls the belt drive motor 61 and the drum drive motor 62 on the basis of the differential circumferential speed which is set.