Patent ID: 8425510

Claim:
A treatment instrument for an endoscope, said treatment instrument comprising: an operation portion; a cylindrical sheath that is connected to the operation portion and that also comprises an insertion portion; an axial electrode that protrudes from and retracts into a distal end opening portion of the sheath by an operation of the operation portion; and a distal end electrode portion that is provided at a distal end portion of the axial electrode; wherein a distal end portion of the sheath includes a tapered portion, the tapered portion being formed in a tapered shape such that a distal end side of the distal end portion is narrower than a proximal end side of the distal end portion, and wherein the tapered portion of the distal end portion of the sheath is formed to satisfy a condition indicated by expression: 0.4c≦d≦0.6c, where an external diameter on the proximal end side of the tapered portion is denoted by “c”, and an external diameter on the distal end side of the tapered portion is denoted by “d”.