A sheet processing apparatus includes: a sheet stacking unit on which sheets are accommodated and stacked as a sheet bundle; an aligning member that is movable along a trailing end, in a conveying direction, of the sheet bundle stacked on the sheet stacking unit and that aligns the trailing end of the sheet bundle in the sheet conveying direction by abutting thereon; a binding unit that moves along the trailing end of the sheet bundle in the sheet conveying direction and binds the aligned sheet bundle; and a moving unit that moves the aligning member in the sheet conveying direction. A distance from the trailing end of the sheet bundle in the sheet conveying direction to a binding position is adjusted by moving the aligning member in the sheet conveying direction.