The insertion device has, with the aforementioned advanced side circumferential aspect of the based component and the aforementioned based component which are formed as one unit from single component and the inside perimeter section of the rotary tubular component with the aforementioned basic edge side circumferential aspect of the advanced side ring component and the aforementioned based component which the liquid densely are maintained and the aforementioned inside perimeter section of the aforementioned rotary tubular component the basic edge side ring component which the liquid densely is maintained and. As for the aforementioned insertion device, in a state where the aforementioned advanced side ring component and the aforementioned basic edge side ring component contact with the aforementioned inside perimeter section of the aforementioned rotary tubular component, the moving range regulation section and the aforementioned rotary tubular component which regulate the moving range of the aforementioned rotary tubular component concerning parallel direction the shaft center position regulation section which regulates the shaft center position of the aforementioned rotary tubular component and, have for the aforementioned longitudinal axis and a state where it becomes the same axis, for the aforementioned longitudinal axis.挿入装置は、単一の部材から一体に形成されるベース部材と、前記ベース部材の前記先端側円周面と回転筒状部材の内周部との間を液密に保つ先端側リング部材と、前記ベース部材の前記基端側円周面と前記回転筒状部材の前記内周部との間を液密に保つ基端側リング部材と、を備える。前記挿入装置は、前記先端側リング部材及び前記基端側リング部材が前記回転筒状部材の前記内周部と接触する状態に、前記長手軸に平行な方向についての前記回転筒状部材の移動範囲を規制する移動範囲規制部と、前記回転筒状部材が前記長手軸と同軸になる状態に、前記回転筒状部材の軸中心の位置を規制する軸中心位置規制部と、を備える。
