An image forming apparatus includes an image forming mechanism, a transfer mechanism including a first endless belt receiving a toner image formed on an image carrier and a second endless belt receiving the toner image formed on the first endless belt, a first detector to detect a speed of movement of the first endless belt or a toner image transferred at a predetermined position on the first endless belt, a belt speed adjustment unit to adjust a speed of movement of the first endless belt based on results obtained by the first detector, a second detector to detect the toner image transferred at a predetermined position on the second endless belt, and a transfer adjustment unit to adjust a speed of movement of the second endless belt based on results obtained by the second detector.