A sheet processing device for stacking one or more sheets temporarily on a stacking unit, and stapling the sheets by a stapling unit after aligned by an alignment unit. The device includes a shift unit that shifts the sheet in both a sheet conveying direction and a direction orthogonal to the sheet conveying direction, and a control unit that controls a shift amount of the shift unit so that an alignment distance of a width direction alignment unit to align the sheet in the direction orthogonal to the sheet conveying direction is constant regardless of a staple position and a sheet size, when stacking the sheets on the stacking unit.