PURPOSE: To contrive the mechanical rigidity of a superconductive magnet device and the improvement in the reliability of the electric insulation thereof by axially providing a plurality of fluid passages between stabilizers making contact with superconductor and so providing a number of holes as to pass from the fluid passages through the stabilizer.

CONSTITUTION: A turn insulator 2 is formed on the outside of a stabilizer 7 such as copper or the like mounted on the outside of a superconductor 1, a plurality of cryogenic refrigerant fluid passages 8 are axially formed in the surface making contact with the superconductor 1 in the stabilizer 7, and there are formed projections 7a making contact with the superconductor 1 between the passages 8 of the stabilizer 7, recesses 8a passing the passages 8 as provided at the projections 7a, and a number of rectangular holes 9 passing the stabilizer 7 and the turn insulator 2 to externally communicate the passages 8. In this manner the mechaical rigidity of the superconductive magnet device can be enhanced, and the electrically insulating reliability thereof can be remarkably raised.