Abstract: A paper binding instrument for binding a sheaf of papers without the use of metal staples including punching edges and auxiliary punching edges. The punching edges can make small holes in a sheaf of paper continuing from punched foot parts of a small width and punched head parts of a large width. The punching edges push down head pieces which were the head parts through the sheaf of papers while leaving punched pieces corresponding to the foot parts. The auxiliary punching edges can make auxiliary small holes facing in different directions from the facing directions of the small holes that are formed with the punching edges.