PURPOSE: To annihilate the stress concentration at branch inlets and increase the mechanical strength of holding member by so constituting the superconductive coil that the inlets of the cooling medium path branches provided to the holding member teeth of a superconductive disc do not mutually oppose.

CONSTITUTION: A superconductive disc 2 comprises providing plural coil grooves 5a on both side faces of a holding member 5, containing superconductive wires 6 in the grooves 5a and filling a cooling medium 7 in the space of their circumferences. Spacing members 8 hold the wires 6 and there are holding member teeth 9 between the grooves 5a. The cooling medium paths 10 formed in the teeth 9 are communicated with each other with each section partitioned by the members 8 by way of branches 10b to discharge the air bubbles produced in the cooling medium 7 to the outside. There are branch inlets 102, 103 at the portions where the branches 10b contact the paths 10 and these are so constituted as not to oppose with each other. At the time of exciting the superconductive coil, stresses are produced in the holding member 5 of the disc 2, but the branch inlets 102 and 103 do not mutually oppose and therefore stress concentration at these portions does not occur.