An image forming apparatus includes an image bearing member, a rotatable transfer roller, a contact separation unit, a driving force transmission portion, a cleaning member, and a control portion. The cleaning member cleans the transfer roller in: (i) a first mode in which the transfer roller rotates with a first peripheral velocity difference while the transfer roller is in contact with the image bearing member, and (ii) a second mode in which the transfer roller rotates with a second peripheral velocity difference while the transfer roller is separated from the image bearing member. The control portion controls a voltage applied to the cleaning member such that a value of the voltage in the first mode or the second mode, which has a smaller peripheral velocity difference between the first peripheral velocity difference and the second peripheral velocity difference, is smaller than the value of the voltage in the other mode.