An image forming apparatus comprising first and second image bearing members, an intermediate transfer belt, a secondary transfer unit, a belt contacting and separating unit, a supporting member, and a separating unit, wherein, when the toner images are primarily transferred from the first and second image bearing members onto the intermediate transfer belt in a state where the intermediate transfer belt is in contact with the first and second image bearing members, the separating unit separates the supporting member from the intermediate transfer belt, and when the toner image is primarily transferred from the second image bearing member onto the intermediate transfer belt in a state where the intermediate transfer belt is away from the first image bearing member, the supporting member supports an inner surface of the intermediate transfer belt between the first and second image bearing members.