A sheet stacking apparatus includes a stacking unit on which a sheet bundle is to be stacked, a lifting unit that can lift and lower the stacking unit, and an air blower unit that can apply air to a side face of the sheet bundle via an air blowing port. The stacking unit further includes a stacking face that comes into contact with and holds a lowermost sheet of the sheet bundle, and a support portion that supports a portion of the stacking face near an end portion thereof, and has a face that is not parallel to the stacking face. The support portion includes a ventilating portion that allows air blown out by the air blower unit from a portion of the air blowing port to pass through the ventilating portion, the portion of the air blowing port being below the stacking face.