Die pressing member 44 includes a first opening 44b1 opening inside the mouthpiece 11 of the endoscope 2 , and the second opening 44b2 can be connected to a fluid source communicating with the first opening 44b1, the first opening 44b1 No. covering a portion of the cavity 44b3 that communicates with the second opening 44b2, a cylindrical portion 44g which is formed from the first opening 44b1 to a predetermined position PL, to cover another part of the cavity 44b3, from a predetermined position PL second and has a narrowed portion 44e having side outer diameter increases toward the opening 44b2, on the outer surface of the diaphragm portion 44e, a plurality of grooves 44f formed over from the predetermined position PL in a predetermined range . .口金押圧部材44は、内視鏡2の口金11の内部で開口する第1開口44b1と、第1開口44b1に連通し流体供給源に接続可能な第2開口44b2と、第1開口44b1と第2開口44b2に連通する空洞部44b3の一部を覆い、第1開口44b1から所定位置PLまで形成された筒状部44gと、空洞部44b3の他の一部を覆い、所定位置PLから第2開口44b2に向かって外径が大きくなる側面を有する絞り部44eと、絞り部44eの外表面上に、所定位置PLから所定範囲に亘って形成された複数の溝44fを有する。
