PURPOSE: To prevent shift of a superconductive coil and to avoid occurrence of a quenching phenomenon by a construction wherein a spacer for forming a cooling medium passage is interposed between the wall faces of a cryocase and both end faces of a mold type superconductive coil in a manner that it is bonded rigidly to the faces of both members.

CONSTITUTION: Spacers 18 each having a spiral-like groove 17 on its one side are interposed between side walls 15a, 16a of a coil accommodating portion 13a of a cryocase and a superconductive coil 14a in a manner that they are bonded to both members with adhesives. A bolt 20 is inserted between the side walls 15a and 16a to rigidly fasten both side walls. With this, the superconductive coil and the side walls of the cryocase are integrated completely to eliminate any gap between them, so that the superconductive coil is immobile even if a force caused by the magnetic field is applied to it.