A sheet stacking tray includes a first stacking portion, a second stacking portion, and a base portion. In a sheet widthwise direction perpendicular to the sheet discharge direction, the first stacking portion includes a first sheet stacking surface having a first stacking width within a range from one half of a sheet width of a maximum-size sheet to be discharged up to the sheet width of the maximum-size sheet. The second stacking portion includes a second sheet stacking surface having a second stacking width smaller than the first stacking width. A border between the first stacking portion and the second stacking portion lies on a discharge-direction upstream side of a contact point where a leading end portion of the maximum-size sheet comes into contact with the sheet stacking part while the sheet is discharged.