An insertion body includes a base arranged in the central axis, a rotating body on an outer periphery of the base to be rotatable around the central axis, and capable of rotating the rotation unit on an external side of the rotating body according to rotation of the rotative force transmitting section of the rotative force transmission unit provided on an inner side of the rotating body around the longitudinal axis, and a channel which includes a guide provided at the base such that the rotative force transmitting section is able to be guided between a first position in which the rotative force transmitting section in the longitudinal axis is able to be inclined from the central axis when the rotative force transmission unit is inserted from the outside to the inside and a second position in which the rotative force transmitting section in the longitudinal axis is parallel to the central axis and a rotative force is able to be transmitted to the rotating body from the rotative force transmitting section, and through which the rotative force transmission unit is inserted through the opening end and the guide.
