An image forming apparatus performs primary transfer of single-color toner image onto an intermediate transfer belt and performs secondary transfer of the toner image onto a sheet, and includes: single image forming unit forming the single-color toner image; single toner supply bottle containing replenishment toner; and first and second support members supporting the belt. The image forming unit is closer to the first member than the second member in a belt rotation direction. The bottle includes: single bottle body; and supply unit near one end of the body in the rotation direction. The other end is (i) closer to the second member than the one end is in the rotation direction and (ii) distant from the image forming unit in a support member direction from the first member toward the second member by one to three times a length of the image forming unit in the support member direction.