An image forming apparatus and a method of controlling the same is provided. A plurality of cells formed at the surface of a transfer roller is filled with a developing agent to initialize the transfer roller, thereby suppressing contamination and electrical non-uniformity of the transfer roller. A method of controlling an image forming apparatus includes determining whether a transfer roller mounted in the image forming apparatus is a new one and, upon determining that the transfer roller is a new one, feeding a developing agent to the surface of the transfer roller and filling a plurality of cells formed at the surface of the transfer roller with the developing agent to initialize the transfer roller.