PURPOSE: To reduce a leakage magnetic flux to be introduced into a stator core end by mounting a superconducting material in a ring shape in gaps between the outer periphery of a ring and the inner periphery of a stator coil at the end of the core.

CONSTITUTION: A superconducting material is mounted in a ring shape on the inner periphery of a stator coil 1. Thus, a leakage magnetic flux 9 generated from a rotor side is shielded by the superconducting material 5 to eliminate the introduction of the magnetic flux 9 to a stator core 2, an end duct 3 and an end plate 4. As a result, it can prevent the iron loss and the heat generation of the end.