Sheet treating apparatus and image forming apparatus having the same

A sheet treating apparatus for effecting treatment on a sheet, comprising:

• a transport rotary member, which transports a sheet;
• a first sheet stacking portions, which temporarily stacks the sheet transported by said transport rotary member, said first sheet stacking portion dropping the sheet after the treatment is effected on the sheet;
• a pair of delivery rotary members, disposed downstream of said transport rotary member, which deliver the sheet transported by said transport rotary member;
• and
• a second sheet stacking portion positioned substantially vertically under said first sheet stacking portion, which supports a sheet directly delivered by said pair of delivery rotary members or a sheet dropped after the treatment in said first sheet stacking portion is completed,
• wherein said first sheet stacking portion comprises a sheet transport path between said transport rotary member and said pair of delivery rotary members, and a sheet supporting portion provided downstream of said pair of delivery rotary members and movable between a sheet stacking position and a retreat position,
• wherein said pair of delivery rotary members is movable between a first position in which said pair of delivery rotary members delivers the sheet and a second position in which rotary members of said of delivery rotary members are separated from each other,
• wherein when said pair of delivery rotary members is in the first position and when said sheet supporting portion is in the retreat position, the sheet is directly stacked on said second sheet stacking portion, and
• wherein when said pair of delivery rotary members is in the second position and when the sheet supporting portion is in the sheet stacking position, the treatment is effected on the sheet.