To provide a superconducting flywheel device for power storage which can secure the safety by arranging magnetic bearing parts above and below a flywheel and also can improve the efficiency by separating a flywheel part and a vacuum vessel for cryogenic temperatures.

The superconducting flywheel device for power storage, the rotating shaft of whose flywheel is supported by a magnetic bearing composed of a superconducting coil and a superconducting bulk body and which has a motor-generator, has a low vacuum vessel 11 for suppression of windage loss where the flywheel 13 is put. The rotating shaft 8 of the flywheel 13 is supported by magnetic bearings which are constituted of superconducting coils 4, 4' and superconducting bulk bodies 9, 9' being arranged pair by pair in the vacuum vessels 7, 7' for cryogenic temperatures arranged above and below across the flywheel 13. The connection between respective vacuum vessels is sealed with a magnetic seal unit which seals the circumference of the rotating shaft with an O-ring of magnetic fluid, and it also has a cooling chamber 15, which cools the motor-generator above the rotating shaft 8.

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