Sheet post-processing device, paper-made staple used in the device, and image forming device provided with the sheet post-processing device

A sheet post-processing device comprising:

• a stacker section that temporarily stores, in a substantially vertical attitude, the paper sheets as a paper sheet bundle;
• a movable stopper that regulates the sheet bundle carried into the stacker section;
• a binding section that binds the paper sheet bundle regulated in position by the stopper;
• a folding section that folds the paper sheet bundle bound by the binding section at a predetermined folding position of the paper sheet bundle;
• and
• a controller that controls movement of the stopper, wherein
• the binding section binds the paper sheet bundle with a paper-made staple, the paper-made staple including leg portions penetrating the paper sheet bundle and then bent inward, a connection portion connecting the leg portions, and a bonding portion that bonds the bent leg portions,
• the folding section includes a folding blade that moves toward the folding position of the paper sheet bundle which substantially corresponds to a center of the paper sheet bundle in a sheet conveying direction, in such a direction as to fold the paper sheet bundle and a pair of folding rollers that nip therebetween the paper sheet bundle folded by the folding blade, and
• the controller controls the stopper portion such that a position of the paper sheet bundle is set such that sheet penetration positions of the leg portions of the paper-made staple sandwich therebetween the folding position.