A rotary shaft (18), the bending operation knob (4), a fixed shaft (10), and two movable disks (11, 12), and the fixed disk (14), a cam member (15), the resistor and imparting member (17), comprising a locking lever (5), the resistance imparting member (17), the protruding cam member which has moved with the rotation in one direction of the cam member (15) (15) by abutting Womotte biasing force against the inner circumferential surface parts (15t), swingably pivoted position of the cam member (15) in a radial direction to secure the second position of the movable disk (11, 12) It has oscillating unit (17t).回動軸(18)と、湾曲操作ノブ(4)と、固定軸(10)と、2枚の可動ディスク(11、12)と、固定ディスク(14)と、カム部材(15)と、抵抗付与部材(17)と、固定レバー(5)と、を具備し、抵抗付与部材(17)は、カム部材(15)の一方向への回転に伴って移動してきたカム部材(15)の突出部(15t)の内周面に対して付勢力を以て当接することにより、カム部材(15)の回動位置を可動ディスク(11、12)の第2の位置において固定する径方向に揺動自在な揺動部(17t)を有している。
