A sheet stacking device including a stacking tray, an auxiliary tray, and pivot limiting means. The stacking tray is disposed to be pivotable relative to an apparatus main body. The stacking tray has a stacking surface on which sheets discharged from discharging means are stacked. The auxiliary tray is pivotable between a storage position at which the auxiliary tray is stored in the stacking tray and a pivot position to which the auxiliary tray pivots from the stacking tray. Pivot limiting means limits pivoting of the auxiliary tray from the pivot position when the stacking tray is caused to pivot.