A sheet stacking apparatus includes a discharge unit, a stacking portion on which discharged sheets are stacked, a lifting unit, and first and second abutting portions. The lifting unit lifts and lowers the stacking portion. The first abutting portion abuts a trailing end of the stacked sheets in a sheet discharge direction. The first abutting portion does not move in an up-down direction. The second abutting portion abuts the stacked sheets trailing end. The first abutting portion supports the second abutting portion such that the second abutting portion is movable in the up-down direction. If the stacking portion is lowered from a first to a second position below the first position, the second abutting portion does not move in accordance with the stacking portion. If the stacking portion is further lowered beyond the second position, the second abutting portion moves in accordance with the stacking portion.

A sheet stacking apparatus includes a discharge unit, a stacking portion on which discharged sheets are stacked, a lifting unit, and first and second abutting portions. The lifting unit lifts and lowers the stacking portion. The first abutting portion abuts a trailing end of the stacked sheets in a sheet discharge direction. The first abutting portion does not move in an up-down direction. The second abutting portion abuts the stacked sheets trailing end. The first abutting portion supports the second abutting portion such that the second abutting portion is movable in the up-down direction. If the stacking portion is lowered from a first to a second position below the first position, the second abutting portion does not move in accordance with the stacking portion. If the stacking portion is further lowered beyond the second position, the second abutting portion moves in accordance with the stacking portion.