A tissue excision instrument that includes a sheath having a lumen, a manipulation member movably disposed inside the lumen, a snare wire coupled to a distal end of the manipulation member, and a holder provided at a distal portion of the sheath and configured to have a through-hole. The snare wire includes a first wire portion that has a first proximal portion including one end and a first distal portion, a second wire portion that has a second proximal portion including the other end and a second distal portion, extends through a through-hole between the second proximal portion and the second distal portion, and extends across the first wire portion, and a curved portion that extends to be curved between the first distal portion and the second distal portion and has at least a part disposed on a distal side relative to the through-hole.
