To improve accuracy of sheet loading height on a tray.

In a sheet processing device including a sample tray 601 and a stack tray 600 discharging and loading a sheet or a bundle of sheets selectively done a designated process and capable of moving up and down, and detecting an uppermost sheet on each tray by sheet surface detection sensors S604, S605 arranged in a lower side of an adjacent of an each sheet discharging opening to the trays to control movement of each tray for always maintaining the uppermost sheet at a same position, for example, a sheet loading height H capable of loading on the sample tray 601 is in a range of the sheet discharging opening of each tray, and a sheet loading height before reaching the sheet loading height capable of loading on the tray is detected.