Provided is opened to the side of the distal end portion 6, a distal end opening 40 of the treatment instrument insertion channel, a position facing the tip opening 40 of the treatment instrument insertion channel, a treatment instrument projecting from the distal end opening portion 40 With the raising of the treatment instrument elevator base 30, the guide wire 50 is provided and a treatment instrument elevator base 30 to be guided to a desired position the tip of, protruded from the distal end opening portion 40, the treatment instrument elevator base 30 When, by contacting the insulating member 35 positioned between the wall portion 40b of the first located along the insertion direction S of the end opening portion 40, the base end of the insertion direction S of the front end opening 40, and disengaging I lock freely.先端部6の側面に開口された、処置具挿通用チャンネルの先端開口部40と、処置具挿通用チャンネル内の先端開口部40に臨む位置に設けられた、先端開口部40から突出した処置具の先端を所望の位置へと誘導する処置具起上台30と、を具備し、先端開口部40から突出されたガイドワイヤ50は、処置具起上台30の起上に伴い、処置具起上台30と、先端開口部40の挿入方向Sに沿って位置する第1の壁部40bと、先端開口部40の挿入方向Sの基端側に位置する絶縁部材35とに当接することにより、係脱自在に係止する。
