An image forming apparatus transfers a toner image, which has been formed onto an image carrying member, to a printing medium. The image forming apparatus includes a sub-scan distance measuring part configured to measure a distance along a sub-scan direction from a predetermined position on the printing medium to a position at which the toner image is transferred to the printing medium; and a toner supplying amount control part configured to control, according to the distance measured by the sub-scan distance measuring part, a toner supplying amount used when the toner image is formed onto the image carrying member.