A stapler clincher mechanism which bends two leg portions of a staple struck and penetrated through papers by a staple driving unit, includes: two first clinchers respectively disposed downwardly of the two leg portions of the staple and respectively including guide inclined surfaces which guides the two leg portions in such a manner that the two leg portions are curved inwardly; a second clincher interposed between the two first clinchers and including a projection portion which presses leading ends of the two curved leg portions toward a paper surface of the papers; and a drive mechanism, after the two leg portions of the staple are curved by the guide inclined surfaces, which retreats the first clinchers along the paper surface and moves the second clincher toward the paper surface.