A spool has a cylindrical outer shape extending in an axial direction intersecting an upward/downward direction, the spool having an outer circumferential surface in which a plurality of annular groove portions extending in a circumferential direction are formed with a space being interposed between the plurality of annular groove portions in the axial direction, a superconducting coil being wound and accommodated inside each of the plurality of annular groove portions. A cover portion is attached to the spool so as to cover each of the plurality of annular groove portions, the cover portion and the plurality of annular groove portions forming a plurality of annular flow paths for refrigerant to cool the superconducting coil. One or more communication paths extend in parallel with the axial direction to communicate adjacent annular flow paths of the plurality of annular flow paths with each other.