This medical instrument includes a first connecting member having a first rotation transmitting portion rotatable about a first axis, a first connecting member fixed to the first arm, a second connecting member rotatable about the second axis A second connecting member having a rotation transmitting portion and fixed to the second arm portion, a third connecting member rotatable about the first shaft and rotatable around the second shaft, And a third rotation transmitting portion rotatable about a third axis. The first rotation transmitting portion and the second rotation transmitting portion are connected so as to rotate in conjunction with each other. The third connecting member is provided at the end portion of the third connecting member and is connected to the third rotation transmitting portion so as to be rotated around the first shaft or the second shaft in conjunction with the third rotation transmitting portion A fourth rotation transmitting portion.この医療器具は、第一軸を中心に回動可能な第一回転伝達部を有し、第一腕部に固定された第一接続部材と、第二軸を中心に回動可能な第二回転伝達部を有し、第二腕部に固定された第二接続部材と、第一軸を中心に回動可能でありかつ前記第二軸を中心に回動可能な第三接続部材と、第三軸を中心に回動可能な第三回転伝達部と、を有する関節部を備える。第一回転伝達部と第二回転伝達部とは、互いに連動して回動するように接続されている。第三接続部材は、第三接続部材の端部に設けられ、第三回転伝達部と連動して第一軸または第二軸を中心に回動するように第三回転伝達部に接続された第四回転伝達部を有する。
