An image forming apparatus, including an image forming part which forms an image on a printing medium, a main feeding part which accommodates the printing medium and supplies the printing medium to the image forming part, and a reversing part which transfers the printing medium, on which an image is formed on a first surface thereof in the image forming part, to the main feeding part, wherein the main feeding part includes a feeding roller part which re-feeds the printing medium, having been transferred through the reversing part, to the image forming part.