Disclosed herein is an image forming system including: an image forming unit for forming images based on a plurality of document pages on a plurality of recording media to form a printed matter; a special sheet feeding unit for storing a special sheet group constituting one set in which a plurality of different types of special sheets are arranged in a predetermined order; a special sheet setting input unit for accepting the number of the special sheets constituting the one set and a page of which the special sheet is inserted into the plurality of recording media; a division setting input unit for accepting an instruction for dividing the printed matter into a plurality of groups by carrying out a post-processing for the printed matter; and a control unit for setting a special sheet inserted into a first place in each of the plurality of groups to a special sheet arranged at a top of the one set when the special sheet setting input unit accepts the page of which the special sheet is inserted and when the division setting input unit accepts the instruction for dividing the printed matter into the plurality of groups.