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.