PURPOSE: To increase mechanical strength and cooling effect and increase superconduction electrical supply current capacity by providing a spool for coil-shaped superconducting wires and coils, which are formed into one piece by resin, and disposing a groove and a hole which serve as fluid helium passage on the spools.

CONSTITUTION: A plurality of grooves 6 and holes 4 for cooling a superconducting wire 1 are provided on a spool 5 for winding the superconducting wire 1. The superconducting wire l wound into the shape of a coil is formed into one piece with the spool 5. With the above construction, the superconducting wire 1 and the spool 5 are monolithically solidified by a resin 2 and the mechanical strength is increased as a whole. A small amount of heat generated in the superconducting wire 1 is cooled by liquefied helium supplied from the grooves 6 and holes 4. Since the superconducting wire 1 is satisfactorily cooled in this manner, the superconduction electric current capacity increases, and a high ampere-turn or magnetic field is generated.