A medical instrument including: an elongated insertion portion having flexibility and being insertable into a living body； a suctional attachment section provided on an outer circumferential surface of the insertion portion at an intermediate position in a longitudinal direction of the insertion portion and having a suction opening at an outer side in a radial direction relative to the insertion portion, opening in the radial direction, and suctionally attaching tissue in the living body； and a rotation mechanism that attaches the suctional attachment section to the insertion portion in such a manner as to be rotatable about an axis in a direction substantially the same as the radial direction.
