A transfer unit includes, as transfer rollers, a first roller and a second roller of which the latter has an elastic layer larger in an axial direction than that of the former, a first bearing member, a second bearing member, a roller holder, a first urging member, a second urging member, a switching cam, a transfer voltage power supply, and a driving mechanism. By rotating the roller holder, one of the first and second rollers is arranged opposite an image carrying member and, by rotating the switching cam, the first or second roller arranged opposite the image carrying member is arranged either at a reference position at which, by being kept in pressed contact with the image carrying member, the first or second roller forms a transfer nip or at a released position at which the first or second roller lies away from the image carrying member.