The present invention is to provide a tissue excision instrument used for medical purposes such as diagnosis, curing, or examination of a living body and excellent in operability. A cylindrical blade part has an annular-shaped blade edge externally sharpened such that the diameter thereof is reduced more toward the tip relative to a diameter d of a blade part body. The blade edge has three curved parts provided at equal intervals along the circumference. The curved parts are irregularities which are formed along the axial direction of the blade part by arc-shaped gentle curves, by which a plurality of arches are formed on the circumference of the blade edge.
