Sheet processsing apparatus and image forming apparatus having such sheet processing apparatus

A sheet processing apparatus having folding means for folding a sheet on which an image was formed and wherein the sheet folded by said folding means is discharged onto a folded sheet stacking portion through a folded sheet discharging port, comprising:

• sheet stacking means provided in a main body of said apparatus for a shifting movement in an up-and-down direction and adapted to stack a sheet discharged from an upper discharging port provided above said folded sheet discharging port without passed through said folding means;
• a shutter member provided in said main body of said apparatus for a shifting movement in an up-and-down direction and adapted to be lifted and lowered upon upward and downward shifting movements of said sheet stacking means to open and close said folded sheet discharging port;
• and
• a pressing member provided on said shutter member and adapted to push the sheet stacked on said folded sheet stacking portion.