Image forming apparatus integrating sheet postprocessing apparatus

A sheet postprocessing apparatus for receiving a sheet discharged from an image forming apparatus and performing a folding process for the sheet, comprising:

• a first crease forming unit which folds the sheet into two by forming a first crease on the sheet in a direction perpendicular to a longitudinal direction thereof;
• a second crease forming unit which folds the two-folded sheet into three by forming a second crease on the sheet so as to be parallel to the first crease;
• a first abutting member which is movable and against which a leading end of a sheet introduced into said first crease forming unit abuts to be positioned;
• a second abutting member which is movable and against which the first crease formed by said first crease forming unit abuts to be positioned;
• a first driving device for driving said first abutting member;
• a second driving device for driving said second abutting member;
• a setting unit to selectively set an inward three-fold process and a Z-fold process;
• and
• a controller for controlling said first crease forming unit, said first driving device, said second crease forming unit, and said second driving device and selecting an inward three-fold process and a Z-fold process so as to make each selected process executable in the same sheet convey path, which guides the sheet to the first crease forming unit and guides the sheet on which a first crease is formed to the second crease forming unit,
• wherein the controller controls the first and second driving devices to move the first and second abutting members at a predetermined position in accordance with the inward three-fold process and the Z-fold process according to the setting operation at the setting unit.