Provided is a sheet stacking apparatus, including: a placement portion on which a sheet is placed; a conveyance portion conveying a sheet placed on the placement portion; a regulation portion regulating a position of a sheet conveyed by the conveyance portion through contact with the sheet; and a pressing portion pressing a sheet regulated in position by the regulation portion, the pressing portion pressing a sheet regulated in position by the regulation portion at a first pressing position and a second pressing position, the second pressing position being spaced apart from the placement portion in a thickness direction of sheets placed on the placement portion by a distance which is longer than a distance between the placement portion and the first pressing position, in which an area of pressing a sheet at the first pressing position is larger than an area of pressing a sheet at the second pressing position.