A medium processing apparatus includes a processing unit that performs processing on a sheet-like medium; an outer wall on which a discharge port, from which the medium processed by the processing unit is discharged, is open; a stacking portion that has a stacking surface on which the medium discharged from the discharge port is stacked; a suction unit that sucks air on the stacking surface via asuction port provided below the discharge port; and a control unit that controls a workload of the suction unit. The control unit reduces the workload of the suction unit according to an open area ofthe suction port which is occluded by the medium stacked on the stacking portion and is decreased.