According to one embodiment, a sheet processing device includes a stapler, a process tray, a first sensor, a second sensor, and a control unit. The stapler performs stapling on the sheet. The process tray places the sheet to be stapled on the upper surface. The first sensor is disposed on the upper side of the process tray. The first sensor outputs a first signal corresponding to a first distance to an object which is disposed at a first position of the process tray. The second sensor is disposed on the upper side of the process tray. The second sensor outputs a second signal corresponding to a second distance to the object which is disposed at a second position on the downstream side in a sheet discharge direction from the first position of the process tray. The control unit controls the stapling using the first signal and the second signal.