To suppress the generation of vibrations at high speed rotation and maintain a stable state not only at rotation of a high speed rotor but also at a standstill.

A rotor is formed by fixing a flywheel on a rotary main shaft to be mounted in a housing on a fixed side of a bearing for supporting the rotor in a non-contact manner. Only one superconductor bearing is contained as a bearing for supporting a lower end side of the rotor in a non-contact manner. The flywheel is composed of a disk part and a cylinder part fixed to or integrally formed with an outer periphery thereof. The cylinder part is arranged to be situated on an outer peripheral side of the superconductor bearing and to cover it.