An insertion portion mounted tool of an insertion instrument includes: ring-shaped members 56, 57 fixed to an outer circumference of an insertion portion 2 an expansion and retraction section 52 provided so as to be movable forward and backward in a longitudinal direction E within a range E1 restricted by the ring-shaped members 56, 57, and configured to be expandable and contractible in a subject by an operation from outside of the subject, and expanded to be held by an inner wall of the subject and rotational movement restriction portions 52at, 55 that restrict an angle in which the expansion and retraction section 52 is rotationally moved in an outer circumferential direction C on the outer circumference of the insertion portion 2.
