PURPOSE: To improve the cooling capacity by storing liquid helium in the central part of a field winding fitting shaft to which a superconductive winding is applied and communicating continuously a liquid supply tube having a projecting tip to the central part from the peripheral section of the fitting shaft through thermal insulation layers.

CONSTITUTION: A field winding 6 of a superconductive line is wound around the peripheral side of an about hollow cylindrical field winding fitting shaft 2. Liquid helium is stored in the internal circumferential surface 3 of a hollow cylindrical section, and a liquid phase section 4 and a gaseous phase section 9 are formed. A liquid supply hole communicating continuously between the peripheral section 8 and the internal circumferential surface 3 of the fitting shaft 2 is provided. A liquid supply tube 10 inserted into the liquid supply hole 5 also projects its tip 12 from the internal circumferential surface 3, and a coolant channel hole 14 is formed on a root section thereof. A thermal insulation layer 11 is provided to the outside of the liquid supply tube 10 in a fitting shaft penetration section, and a thermal insulation layer 15 is provided to the inside of the tube 10 at the tip 12. The heat of coolant of the peripheral section 8 reaches a high temperature through an adiabatic compression process by centrifugal force, and after transferring it to the liquid supply tube 10, it is radiated to the liquid phase section 4. Accordingly, the cooling capacity is improved, and such a rotor having high reliability is obtained.