The treatment instrument, and a treatment instrument is inserted through movably in the channel of the ultrasonic endoscope, having a distal end and a proximal end, and has a cylindrical body, a plurality of dimples recessed outer surface is formed a treatment member each of said plurality of dimples, the distance between the deepest depths of the radial inside of the dimple and the rear end of the most proximal of the dimple in the center axis direction of the treatment member but is shorter than the distance between the deepest part and the front end of the most distal of the dimple in the center axis direction.この処置具は、超音波内視鏡のチャンネルに進退自在に挿通される処置具であって、先端と基端とを有し、円柱状であり、外面に窪んだ複数のディンプルが形成された処置部材を有し;前記複数のディンプルのそれぞれは、前記処置部材の中心軸線方向における前記ディンプルの最も前記基端側の後端と前記ディンプルの径方向内側の最も深い最深部との間の距離が、前記中心軸線方向における前記ディンプルの最も前記先端側の前端と前記最深部との間の距離よりも短い。
