For the purpose of rotating around the longitudinal axis of the long member without operating the treatment portion at the distal end of the long member, the rotating mechanism (1) for a treatment instrument according to the present invention includes a long member (2) and A rotating member (4) supported at the tip of the long member (2) so as to be rotatable around the longitudinal axis of the long member (2), and a treatment instrument (3) fixed thereto； and a long member (2) A tension converting member (5) that is disposed along the distal end, the rotating member (4) is fixed to the distal end, and the tension applied to the proximal end is converted into rotation about the longitudinal axis of the distal end. The wire-shaped power supply member (6) for supplying power for operating the treatment instrument (3) is connected to the rotary member (4) and the tension converting member (5). It has a through hole (5a) penetrating in the direction.長尺部材の先端の処置部を動作させることなく、長尺部材の長手軸回りに回転させることを目的として、本発明に係る処置具用回転機構（１）は、長尺部材（２）と、長尺部材（２）の先端に、長尺部材（２）の長手軸回りに回転可能に支持され、処置具（３）が固定された回転部材（４）と、長尺部材（２）に沿って配置され、先端に回転部材（４）が固定され、基端に加えられた張力を先端の長手軸回りの回転に変換する張力変換部材（５）とを備え、処置具（３）に、処置具（３）を作動させる動力を供給するワイヤ状の動力供給部材（６）が接続され、回転部材（４）および張力変換部材（５）が、動力供給部材（６）を長手軸方向に貫通させる貫通孔（５ａ）を有する。
