A sheet folding apparatus for folding a sheet is provided with a hold member that holds a transported sheet in a substantially cylindrical shape, a shift member that presses the outer circumferential surface of the sheet of the substantially cylindrical shape held by the hold member to make a substantially flat shape, and a discharge section that further presses the sheet made the substantially flat shape by the shift member, while discharging in a direction crossing a transport direction. By this means, it is possible to provide a relatively compact sheet folding apparatus.

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.

A sheet folding apparatus for folding a sheet is provided with a hold member that holds a transported sheet in a substantially cylindrical shape, a shift member that presses the outer circumferential surface of the sheet of the substantially cylindrical shape held by the hold member to make a substantially flat shape, and a discharge section that further presses the sheet made the substantially flat shape by the shift member, while discharging in a direction crossing a transport direction. By this means, it is possible to provide a relatively compact sheet folding apparatus.

A sheet processing device includes: a folder that forms a plurality of folds on a sheet such that a fold part and a part with no fold of the sheet overlap with each other; a conveyance unit that conveys the sheen on which the folds are formed by the folder; and a pressing part that presses the fold part of the conveyed sheet in which the fold part and the part with no fold overlap with each other, from a side on which the fold part is located.