The endoscopic high-frequency treatment instrument includes a sheath formed of an insulating material is formed of a material having conductivity, a shaft-like member which is inserted to allow advance and retreat within the sheath, is fed into the sheath the fluid can be jetted to the front pipe is formed, and an electrode connected to the distal end of the shaft-like member, the electrode, the outer peripheral surface take action by energizing the in contact with tissue and when the supply of the fluid and has an inner peripheral surface of the pipe facing the fluid, the arithmetic mean roughness of the outer peripheral surface is greater than the arithmetic mean roughness of the inner peripheral surface, and an arithmetic average roughness of the inner peripheral surface, 0.1 m or less It is.この内視鏡用高周波処置具は、絶縁性を有する材料で形成されたシースと、導電性を有する材料で形成され、シース内に進退可能に挿通された軸状部材と、シース内に供給された流体を前方に噴出可能な管路が形成され、軸状部材の先端部に接続された電極とを備え、電極は、接触した組織に通電して処置を行う外周面、および流体の供給時に流体に面する管路の内周面を有し、外周面の算術平均粗さは、内周面の算術平均粗さよりも大きく、かつ、内周面の算術平均粗さは、0.1μm以下である。
