An image forming apparatus includes an intermediary transfer belt, first to third image bearing members, a driving member, and first and second drive transmission members, and includes first to third transfer positions. A first inter-transfer-position distance between the first and second transfer positions and a second inter-transfer-position distance between the second and third transfer positions are different from each other. The first inter-transfer-position distance is set at “N×A” and the second inter-transfer-position distance is set at “N×A±N×A/i”, where N is an integer of rotations of the driving member during to movement of the belt in the first inter-transfer-position distance, A is a distance of movement of the belt when the driving member rotates through one full circumference, and i is a transmission ratio between the first and second drive transmission members.