PROBLEM TO BE SOLVED: To provide a surgical instrument that can be downsized by increasing a degree of freedom in the arrangement of a driven member.SOLUTION: A surgical instrument 40 is a surgical instrument 40 removably connected to a robot arm 21 of a robot surgical system 100 and includes: a substrate 43; a treatment instrument 41; a slender shaft 42, in which its proximal end 42a is arranged in the substrate 43, and the treatment instrument 41 is arranged at its distal end 42b; a driven member 44 provided to the substrate 43 so as to be rotatable around a rotation shaft; a bearing-incorporating pulley 46; and a wire W whose end is wound and fixed around the driven member 44 through the shaft 42 for operating the treatment instrument 41. The wire W is wound and fixed around the driven member 44 from the shaft 42 through the bearing-incorporating pulley 46.SELECTED DRAWING: Figure 7COPYRIGHT: (C)2020,JPO&INPIT【課題】被駆動部材の配置の自由度を大きくすることにより小型化することが可能な手術器具を提供すること。【解決手段】この手術器具40は、ロボット手術システム100のロボットアーム21に取り外し可能に接続される手術器具40であって、基体43と、処置具41と、近位端42aが基体43に配置され、遠位端42bに処置具41が配置された細長いシャフト42と、基体43に対して回転軸を中心に回転可能に設けられる被駆動部材44と、ベアリング内蔵プーリ46と、処置具41を操作するためにシャフト42を介して被駆動部材44に端部が巻き止められるワイヤWと、を備える。そして、ワイヤWは、シャフト42からベアリング内蔵プーリ46を介して被駆動部材44に巻き止められている。【選択図】図7