An image forming system includes an input unit for input of setting information, an image forming unit, a conveying unit, a control unit, and a jam detecting unit, wherein a set of a plurality of different kinds of special sheets disposed in a predetermined order is used. When occurrence of a jam is detected by the jam detecting unit, the control unit recognizes whether a special sheet having been fed is present in the image forming system, and if it is recognized that a special sheet is present in the image forming system, the control unit controls the conveying unit, after the jam being released, to eject a special sheet or sheets as unnecessary up to one that is disposed preceding a special sheet that is of the same kind as a most front one that was present in the image forming system at the time of the occurrence of the jam.