An annular member (56, 57) fixed to the outer periphery of the insertion portion (2), and an annular member (56, 57) which is provided movably in the longitudinal direction E within a range E 1 regulated by the annular member (56, 57) A retraction section (52) which is expandable and contractible within the subject by an operation from the outside and locked to the inner wall of the subject after expansion, and a retraction section (52) is rotated in the outer circumferential direction C on the outer circumference of the insertion section (2) And a rotation regulating portion (52 at, 55) for regulating the moving angle. 挿入部（２）の外周に固定される環状部材（５６、５７）と、環状部材（５６、５７）によって規制された範囲Ｅ１内において長手方向Ｅの前後に移動自在に設けられるとともに、被検体外からの操作によって被検体内で拡縮自在であり拡張後に被検体の内壁に係止される圧排部（５２）と、挿入部（２）の外周において圧排部（５２）が外周方向Ｃに回動する角度を規制する回動規制部（５２ａｔ、５５）と、を具備する。
