A transfer unit includes first and second rollers of which the second roller has an elastic layer larger in the axial direction than the first roller, a roller holder, and a switching cam. One of the first and second rollers is, by rotating the roller holder, arranged opposite an image carrying member and, by rotating the switching cam, arranged selectively either at a reference position to form a transfer nip or at a released position to lie away from the image carrying member. Let a length of the elastic layer of the first roller in the axial direction, a width of an effective image area on the image carrying member to which a toner image can be transferred, and a width of a recording medium of a maximum size allowing transfer using the first roller be L1, L3, and L4 respectively, L4