An image forming apparatus including a case, a printing medium feeding unit disposed in the case to feed printing media, an image forming unit disposed in the case to form images on a printing medium fed from the printing medium feeding unit using developer and to include at least one portion being stained when the images are formed, and a control portion to control the image forming unit to form the images in a plurality of print modes. The control portion sends a cleaning command to clean the at least one stained portion when the amount of the developer used by the image forming unit reaches a reference amount of the developer or when the number of the printing media supplied by the printing medium feeding unit reaches a reference value of the number of the printing media.