A treatment instrument for treating a biological tissue has a first axis and a first axis each having a longitudinal axis and having a gripping surface capable of gripping the biological tissue therebetween by opening and closing in an opening and closing direction orthogonal to or substantially orthogonal to the longitudinal axis. 2 gripping portions, and an action portion having an edge portion capable of cutting a living tissue by rotating around a central axis that is the same as or substantially parallel to the longitudinal axis, and the edge portion is separated from the first gripping portion. A rotating body that is movable toward the second gripping portion, and a first member that is provided in the first gripping portion and that can guide the edge toward the second gripping portion through a gripping surface of the first gripping portion. The second gripping portion is provided on the guide portion and the second gripping portion, the edge portion can be guided to the second gripping portion through the gripping surface of the first gripping portion, and the second gripping portion is guided through the gripping surface of the first gripping portion. And a second guide portion capable of cutting the living tissue when guiding to the body.生体組織を処置するための処置具は、長手軸を有し、前記長手軸に直交又は略直交する開閉方向に開閉することで生体組織をその間に把持可能な把持面をそれぞれ有する第１及び第２把持部と、前記長手軸と同一又は略平行な中心軸の軸回りに回動することで生体組織を切断可能な縁部を有する作用部を備え、前記縁部を前記第１把持部から前記第２把持部に向かって移動可能な回動体と、前記第１把持部に設けられ、前記第１把持部の把持面を通して前記第２把持部に向かって前記縁部を案内可能な第１案内部と、前記第２把持部に設けられ、前記第１把持部の把持面を通して前記第２把持部に前記縁部を案内可能で、前記第１把持部の把持面を通して前記第２把持部に案内する際に前記生体組織を切断可能な第２案内部とを有する。
