PROBLEM TO BE SOLVED: To provide a surgical instrument capable of easily and surely performing a rotating work between a plurality of angular positions and a fixing work at each angular position. A surgical instrument (1) includes a locking structure (115c) configured to be engageable and disengageable in a direction along a rotation axis (11x), with respect to one portion of a connecting portion (11) and rotating portions (12, 13). A locking member 115 configured to be movable in a direction along the rotation axis and having an angular attitude around the rotation axis or another axis parallel to the rotation axis linked to one portion； It is provided on the other part of the rotation part and can receive the locking structure in the direction along the rotation axis corresponding to a plurality of angular positions. The locked structure 12c that is locked in the rotation direction, the locking structure and the locked structure are configured to be disengageable, and the locking position of the locking structure with respect to the locked structure is set along the rotation axis. And a positioning means 116 capable of positioning and holding in the opposite direction. [Selection diagram]【課題】複数の角度位置の間の回動作業や各角度位置における固定作業を容易かつ確実に行うことのできる手術器具を提供する。【解決手段】手術器具１は、回動軸線１１ｘに沿った方向に係脱可能に構成される係止構造１１５ｃを備え、連結部１１と回動部１２，１３のうちの一方の部分に対して、回動軸線に沿った方向に移動可能に構成されるとともに回動軸線若しくは回動軸線と平行な他の軸線の周りの角度姿勢が一方の部分に連動する係止部材１１５と、連結部と回動部のうちの他方の部分に設けられ、複数の角度位置に対応して回動軸線に沿った方向に係止構造を受け入れ可能であり、係止構造の受け入れにより回動軸線の周りの回転方向に係止される被係止構造１２ｃと、係止構造と被係止構造を係脱可能に構成するとともに、係止構造の被係止構造に対する係止位置を回動軸線に沿った方向に位置決め保持可能な位置決め手段１１６とを有する。【選択図】 図３
