SHEET POST-PROCESSING DEVICE AND IMAGE FORMING APPARATUS INCLUDING THE SAME

PROBLEM TO BE SOLVED: To provide a sheet post-processing device that can stack the sheet without compression buckling, resulted in prevention of poor staple processing.SOLUTION: The sheet post-processing device includes a staple tray 16 which stacks the sheet on which image forming is implemented, standard fences 10a and 10b and a second fences 8a and 8b which align the sheet, a stapler 11 which files the sheet, and a sheet compression buckling prevention means which prevents the compression buckling of the sheet when stacks the sheet to the staple tray 16. The sheet compression buckling prevention means consists of a projection member 25 which carries out a stack the sheet concerned that is sagged in the shape of an arc of cross section by projecting from the sheet loading surface of the staple tray 16 to abut to a part of the sheet and a migratory mechanism which moves the projection member 25 between the position projected from the sheet loading surface of the staple tray 16 and the position which does not interfere the sheet. Meanwhile, the projection member 25 is positioned on a position which does not interfere the sheet when the sheet is filed by a stapler 11.