Patent ID: 8672314

Claim:
A sheet stacking apparatus, comprising: a discharging unit configured to discharge a conveyed sheet; a stacking tray on which a sheet discharged by the discharging unit is stacked; an alignment unit configured to align a sheet stacked on the stacking tray in a width direction perpendicular to a direction in which the sheet is discharged, the alignment unit including an alignment member configured to be movable in the width direction, and a first moving unit configured to move the alignment member in the width direction, the alignment member aligning the sheet by coming into contact with a side of the sheet stacked on the stacking tray in the width direction; a detection unit configured to detect a position of a top surface of a plurality of sheets stacked on the stacking tray; a second moving unit configured to vertically move the stacking tray while a plurality of sheets are being stacked on the stacking tray, so that a predetermined distance is maintained between a position detected by the detection unit and a discharge port of the discharging unit; a third moving unit configured to vertically move the alignment member; and a control unit configured to cause, if the second moving unit lowers the stacking tray to a predetermined position while the alignment unit is executing an alignment operation at a first position, the third moving unit to lower the alignment member to a second position lower than the first position and cause the alignment member to execute the alignment operation at the second position.