Sheet processing device and image forming device provided with the sheet processing device

A sheet processing device that saddle stitches and folds in half a paper sheet bundle, comprising:

• a stacker section that temporarily stacks conveyed paper sheets in a substantially vertical attitude;
• a stopper that regulates the paper sheets stacked in the stacker section;
• a first binding section that is provided in the stacker section and saddle-stitches the paper sheet bundle regulated by the stopper at a binding position around a center of the paper sheet bundle in a sheet conveying direction;
• a folding section that folds in half the paper sheet bundle regulated by the stopper at a position around the center of the paper sheet bundle in the conveying direction;
• and
• a conveying section that conveys the paper sheet bundle that has been folded in half by the folding section with a back side of the folded paper sheet bundle as a leading end in the conveying direction, wherein
• the conveying section includes a second binding section that binds the folded paper sheet bundle at the back side thereof with a paper-made staple, and the paper-made staple is driven to straddle the back side of the folded paper sheet bundle.