An insertion apparatus includes an inner guide sheaths 40, a fixing lever 80, and a moving member fixing mechanism 100 that fixes movement of the inner guide sheaths 40, and the moving member fixing mechanism 100 includes a guide member 117, a crank member 110 including a reciprocating portion 110a that is movable as the fixing lever 80 is operated, a pair of link members 115 that is openable and closable around a slider pin 130 as the crank member 110 is moved, and cam members 120 that are rotatable to a second rotation position where the cam members simultaneously press exposed sites 40r to wall surfaces 117w in a vertical direction R, and a first rotation position where the cam members are separated from the exposed sites 40r, by either one of opening and closing of the respective link members 115. 内側ガイドシース４０と、固定用レバー８０と、内側ガイドシース４０の移動を固定する移動部材固定機構１００と、を具備し、移動部材固定機構１００は、ガイド部材１１７と、固定用操作レバー８０の操作に伴い移動自在な往復部１１０ａを有するクランク部材１１０と、クランク部材１１０の移動に伴いスライダピン１３０を中心に開閉自在な一対のリンク部材１１５と、各リンク部材１１５の開閉いずれかにより、露出部位４０ｒを壁面１１７ｗに対して同時に垂直方向Ｒに押し付ける第２の回動位置と、露出部位４０ｒから離間する第１の回動位置とに回動自在なカム部材１２０と、を具備している。
