PURPOSE: To reduce the electric resistance of a connecting part and improve the stability of superconduction, by a method wherein a circumferential groove for connection is provided on the end of a coil mounting shaft and connecting parts between neighboring partial coils are arranged in the groove for connection.

CONSTITUTION: A rotor is constituted of a coil mounting shaft 2 and superconducting field, coils 3, consisting of saddle type partial coils 3a, 3b, 3c which are wound concentrically and fixed to the coil mounting shaft 2. Respective partial coils are constituted of straight parts A, corner parts B and arc parts C. Connecting part 16 is provided between the arc parts C while circumferential groove 18 for connection is formed on the surface of the coil mounting shaft 2 between slots 17 provided on the same shaft 2. The connecting part 16 between the outermost peripheral turn of the partial coil 3a and the innermost peripheral turn of the partial coil 3b is positioned in the groove 18 for connection. The length of the groove 18 for connection is 200 mm or more and the length L of the connecting part 16 may secure a generally required connecting length (about 100 mm) sufficiently.