A belt driving controller is disclosed. The belt driving controller controls driving of a belt that is wound around plural sustaining rollers by controlling a driving sustaining roller that transmits a driving force to the belt. In two sustaining rollers, a calculating method for recognizing a PLD (pitch line distance) of the belt is used. In the calculating method, the delay period during which the belt moves a distance from a driven sustaining roller having a large diameter to a driven sustaining roller having a small diameter is determined to be shorter than before in the belt moving direction.