To obtain a long-length radiation shield by connecting, with rigid welding including less deformation, double cylindrical bodies having an interlayer coolant route in the axial direction.

In the case of forming a long-length body by connecting a plurality of double cylindrical bodies 13 in the axial direction by means of welding, aperture 14 is processed at the external and internal circumferences at the coupling end portions of the double cylindrical bodies 13 and annular groove 15 is processed in the width larger than the width in the radius direction of the coolant route 12 between the apertures 14 at the external and internal circumferences and then apertures 14 are coupled by the welding from both external and internal circumferences to form a long-length radiation shield.