A fusing roller in an image forming apparatus heats and fuses a developed image transferred to a recording medium. A heat generator is controlled to maintain a detected temperature of the fusing roller at a reference fusing temperature until a predetermined time period is elapsed from when a trigger signal for starting preheating provided prior to entry of a print command is entered, and is stopped when the predetermined time period elapses. The fusing roller is rotated while being heated until the detected temperature once reaches the reference fusing temperature, and thereafter the detected temperature is maintained at the reference fusing temperature until the predetermined time period elapses by heating but not rotating the fusing roller.