A sheet stacking device includes a liftable/lowerable sheet stacking portion on which sheets to be ejected are stackable. The sheet stacking portion moves downward as an amount of stacked sheets increases. The sheet stacking device includes a movable member disposed below the sheet stacking portion with a space therebetween, and a detecting portion configured to output a signal in accordance with a position of the movable member. Ejection of the sheet to the sheet stacking portion is stopped on the basis of the signal output from the detecting portion in accordance with downward movement of the movable member.