PURPOSE: To facilitate cooling a machine by composing a superconducting rotor winding of high temperature superconducting material and providing a cooling means which supplies a cooling medium to a rotor from a jetting mechanism.

CONSTITUTION: A superconducting generator is composed of a rotor 21 having a superconducting rotor winding, bearing 22, drive part 23 of the rotor 21, exciter 24, stator 25, housing 26, heat insulating layer 27, etc. While in a fixed side, a jetting mechanism, for instance, nozzle 28 is provided in the periphery of the rotor 21. Further a fluid reservoir 31 of cooling fluid, pump 32, steam reservoir 33 and a liquefying device 35 are provided. A cooling means of the rotor winding enables the cooling medium to be directly blown toward a surface part of the rotor 21 from a fixed part, eliminating the necessity for providing piping inside the rotor and a vacuum for heat insulation.