An image forming apparatus includes a main body of the image forming apparatus with an opening portion, an image forming unit, an accommodation portion, a stack portion, a sheet moving unit, and a control unit that controls switching between a first mode that moves, with the sheet moving unit, a sheet accommodated in the accommodation portion and stops the sheet when a part of the sheet is exposed external to the main body of the image forming apparatus from the opening portion, and a second mode that moves the sheet, with the sheet moving unit, accommodated in the accommodation portion and that discharges the sheet to the stack portion.

A medium processing apparatus includes a first medium support portion that supports a printing medium bundle consisting of printed media on which printing has been performed and an insertion medium inserted between the printed media, a second medium support portion that supports an insertion medium bundle including plural insertion media, and a supply unit that supplies a corresponding insertion medium from the insertion medium bundle to a place where the insertion medium is missing in the printing medium bundle and does not supply an insertion medium corresponding to the insertion medium included in the printing medium bundle among the insertion media included in the insertion medium bundle to the printing medium bundle.

A medium processing apparatus includes a first medium support portion that supports a printing medium bundle consisting of printed media on which printing has been performed and an insertion medium inserted between the printed media, a second medium support portion that supports an insertion medium bundle including plural insertion media, and a supply unit that supplies a corresponding insertion medium from the insertion medium bundle to a place where the insertion medium is missing in the printing medium bundle and does not supply an insertion medium corresponding to the insertion medium included in the printing medium bundle among the insertion media included in the insertion medium bundle to the printing medium bundle.