Manufacturing method of staple-less binding unit

A manufacturing method of a staple-less binding unit that includes a first binding unit that has a plurality of recesses and projections and a second binding unit that is arranged to face the first binding unit and has recesses and projections that fit to the recesses and the projections of the first binding unit and in which mediums are bound by being interposed between the first binding unit and the second binding unit in a thickness direction of the mediums, the method comprising:

• forming the binding units with a die;
• bending an entire portion of each binding unit that has the recesses and the projections by pressing a portion of each binding unit that is on an opposite side to the portion having the recesses and the projections after the binding units are formed and before the center positions are adjusted so that the center positions are arranged at pre-set intervals;
• adjusting center positions of projecting portions of the binding units formed by the die and removed from the die, wherein positions of tip ends of the projecting portions are the center positions;
• and
• adjusting outer shapes of the projecting portions of which the center positions have been adjusted.