A clipping instrument for biological tissues equipped with an outer tube which can be inserted into a biological cavity, an operating member freely passed through the outer tube, an operating wire freely passed though the operating member, a self-opening holder which can be opened and closed by the action of the operating member attached to the edge of the operating wire, and a self-opening clop having a clipping member for clopping a biological tissue which is attached to the edge of the holder in a detachable manner by opening/closing the holder. Using this clopping instrument, a lesion site can be surely clipped over a long period of time in ligating a breeding site in a biological tissue, stitching a laceration, making in excision of a mucosal tissue and so on with an endoscope.