An image forming apparatus has transfer rollers for transferring an unfixed image, fixing rollers with a changeable conveying speed, discharging rollers with a changeable conveying speed thereof and for discharging the recording material on which the image has been fixed by the pair of fixing rollers, a loop detecting sensor for detecting the loop of the recording material between the transfer rollers and of fixing rollers, and a control for changing the conveying speed of the fixing rollers on the basis of the detection of the loop detecting sensor so that the loop of the recording material is maintained with a predetermined range, wherein the control board controls the conveying speed of the discharging rollers so as to become equal to the conveying speed of the fixing rollers after the recording material has passed the transfer rollers.