Clincher holders hold a pair of clinchers for bending the legs of a staple driven by a driver, and have slanting guide faces for guiding the tips of the legs of the staple toward the clinchers. In a stapling table for receiving sheets of paper, an opening is made. The clincher holders are movable inside the opening. Drop-preventing portions for preventing the sheets of paper from dropping inside the opening in stapling are projected from opening edges of the opening toward the inside of the opening.