The braking adjustment body 30 is disposed in a direction orthogonal to the rotation axis between the bending drive shaft 25 and the lock operation shaft 26. The braking adjustment body 30 is configured to include an intermediate member 31 that abuts against the cam portion 26 a of the lock operation shaft 26 and a braking member 40 that applies a pressing force corresponding to the displacement of the intermediate member 31 to the bending drive shaft 25 . In the intermediate member 31, the shaft body portion 32 and the cylindrical sliding portion 33 are screw-coupled, and by rotating the knurled surface of the outer periphery of the sliding portion 33 with tweezers or the like in a state where both are screw-coupled, It is possible to adjust the distance between the proximal end portion and the distal end portion of the member 31. When the fixing force with respect to the bending drive shaft 25 decreases, the distance between the proximal end portion and the distal end portion of the intermediate member 31 It is possible to recover the fixing force by readjusting the distance.湾曲駆動軸25とロック操作軸26との間の回転軸と直交する方向に、制動調整体30を配設する。制動調整体30は、ロック操作軸26のカム部26aに当接する中間部材31と、中間部材31の変位に応じた押圧力を湾曲駆動軸25に与える制動部材40とを備えて構成されている。中間部材31は、軸体部32と筒状の摺動部33とがネジ結合されており、両者をネジ結合した状態で摺動部33外周のローレット面をピンセット等で回転させることにより、中間部材31の基端部と先端部との間の距離を可変して調整することができ、湾曲駆動軸25に対する固定力が低下したとき、中間部材31の基端部と先端部との間の距離を再調整して固定力を回復することができる。
