A clip member of substantially a figure "eight" shape is detachably attached to an instrument body. The instrument body has an outer flexible tube, an actuating tubular member inserted into the outer tube, and a wire inserted into the actuating tubular member. A holder is detachably mounted through a guide member to the forward end portion of the actuating member. To the forward end of the wire is secured a hook member for anchoring the clip member. A pair of clamping portions of the clip member is opened by forcefully engaging a pair of offset portions of the clip member with the inner surface of the holder, and closed by forcefully engaging a pair of intersecting portions with the inner surface of the holder. As a result, any affected portion of a body cavity of a human being is clipped by the clip member associated with the holder. The clip member, together with the holder, is left within the body cavity with the clamping portions thereof closed.