The sheet discharge device includes: a sheet discharge part; a sheet discharge tray having a tray upper surface and a rear wall portion; a fullness detection sensor for detecting that a height of a stack surface of folded sheets; and a first sheet presser member and a second sheet presser member for pressing a rear end side and a fore end side in a discharge direction, of the folded sheet. In a first pressing position in which the first sheet presser member extends from above the detection sensor to below the detection region, and is brought into contact with the folded sheet of a minimum size stacked on the tray upper surface. When a stack number of the folded sheets has exceeded a specified number, the first sheet presser member is retracted upward from the first pressing position by the rise of the stack surface.