MEDIUM PROCESSING DEVICE AND IMAGE FORMING APPARATUS

A medium processing device includes a discharge member, a discharge tray, a shift part and a control part. The discharge member is configured to discharge a medium from a discharge position in a discharge direction. On the discharge tray, the medium is stacked. The shift part is configured to vary a relative position of the discharge position and the discharge tray in a shift direction perpendicular to the discharge direction to shift a shift position where the medium is stacked on the discharge tray. The control part is configured to control the shift part so as to shift the shift position for each medium bundle containing a plurality of the mediums. The control part calculates a thickness of the medium bundle, and when the calculated thickness exceeds a first threshold value, the control part makes it possible to select a number of the shift position from a plurality of candidates.