An image forming apparatus includes a developing unit which develops toner to form an image, a transfer unit which transfers the image onto a printing medium, and a fusing unit to fuse the image transferred onto the printing medium, wherein the transfer unit includes a belt, a plurality of rollers which rotatably supports the belt, and a belt tension applying unit which moves a first roller of the plurality of rollers between a belt tension release position at which a tension of the belt releases and a belt tension applying position at which the tension of the belt applies by the interlocking motion between the belt tension applying unit and a second roller of the plurality of rollers.