An image forming apparatus includes a first image forming unit and a second image forming unit to form first toner images and second toner images, respectively, of different colors, a transfer member to transferred received toner images to a position, and a contact/separation unit to switch between first and second modes. Where a first, second, and third image are formed in order on sheets, the mode is switched from the first to the second mode after the transfer member receives the first image to the transfer member and before formation of the second image by the first image forming unit is started if a first image length in a conveyance direction is smaller than a predetermined length. After the sheet receives the first image, the contact/separation unit switches the mode from the first to the second mode if the first image length is greater than the predetermined length.