An image forming system includes an image forming apparatus including a fixing unit, a folding processing portion, and a pressure-bonding portion. A first recording material having a first basis weight is fixed at a first temperature by the fixing unit and then is pressure-bonded by the pressure-bonding portion after a lapse of a first period. A second recording material having a second basis weight is fixed at a second temperature by the fixing unit and then is pressure-bonded by the pressure-bonding portion after a lapse of a second period. The second basis weight is larger than the first basis weight. The second temperature is higher than the first temperature. The second period is longer than the first period.