Superconducting magnet

The present invention concerns superconducting magnets to be used in a thermonuclear device, and provides a superconducting magnets capable of keeping a predetermined surface pressure without causing slackening between the superconducting magnets and FRP insulation spacers even when electromagnetic force is exerted when used. Namely, the FRP insulation spacers are formed by a combination of a fiber and a resin having a glass transient temperature of from 180 to 200degC and a weight ratio of from 10 to 20%. The combination of the FRP insulating spacers, the superconductors and a vessel is selected so that when the temperature is raised from an ordinary temperature to a working temperature, the volume shrinking amount of the vessel is greater than the volume shrinking amount of a composite member of FRP and the superconductors in the vessel. A plurality of superconductors are disposed each at a predetermined distance in the vessel. The FRP insulation spacers are interposed in close contact between the superconductors and between the superconductors and the vessel wall. They are assembled by a cotter under a compressive surface pressure greater than the electromagnetic force generated in the normal state of superconductive coils. (I.S.)