Patent ID: 8651480

Claim:
A sheet stacking apparatus comprising: a discharge portion which discharges a sheet; a sheet stacking portion on which the sheet discharged by the discharge portion is stacked; an aligning portion which includes a pair of aligning arms and a pair of aligning members, the pair of aligning arms being supported while being downwardly and upwardly rotatable, and movable in a width direction orthogonal to a discharge direction of the sheet, the pair of aligning members being supported at a leading end of the pair of aligning arms while being downwardly and upwardly rotatable; a driving portion which rotates the pair of aligning arms and moves the pair of aligning arms in the width direction; and a controller which controls the driving portion, when the sheet discharged by the discharge portion is aligned in a position which is offset in the width direction with respect to the sheet previously stacked on the sheet stacking portion, so that the driving portion rotates the pair of aligning arms downwardly to rotate one of the pair of aligning members upwardly by abutting on an upper surface of a sheet previously stacked on the sheet stacking portion, and so the discharged sheet is aligned with the sheet previously stacked in the width direction by the one of the pair of aligning members and the other which does not abut on the sheet previously stacked on the sheet stacking portion.