PURPOSE: To miniaturize a rotor, and to simplify its structure by feeding a gas into a heat-insulating vacuum layer and bringing a liquid-phase refrigerant to an easily vaporized state when stopping operation.

CONSTITUTION: A superconducting rotor is connected to a liquid-phase refrigerant feeder through a liquid-phase refrigerant supply pipe 1a for a refrigerant suction and exhaust evacuator 1 and to a vapor-phase refrigerant recovery device through a vapor-phase refrigerant exhaust pipe 1b respectively, and connected to an evacuation valve 10 and a gas injection valve 13 juxtaposed through a gas path 1c. The evacuation valve 10 is connected to a vacuum pump 11 evacuating heat-insulating vacuum layers 9 for the rotor, and the gas injection valve 13 is connected to a gas source 14 for a dry nitrogen tank supplying the heat-insulating vacuum layers 9 with dry vapor-phase nitrogen. Consequently, when a superconducting rotary electric machine is shut down, the supply of a liquid-phase refrigerant 3 is stopped, the evacuation valve 10 is closed, the gas injection valve 13 is opened and the heat-insulating vacuum layers 9 are supplied with dry vapor-phase nitrogen. Accordingly, penetrating heat is increased largely, and the evaporation of the liquid-phase refrigerant 3 is promoted and the liquid-phase refrigerant 3 is discharged in a short time.