PURPOSE: To make the cracking and releasing in an impregnating resin hardly occur by a method wherein the electromagnetic stress imposed on the impregnating resin between coil conductors is to be lightened.

CONSTITUTION: Within the superconducting coil 1 having no bobbin at all closely wound up with a superconducting wire 2 to be impregnated with an epoxy resin 5, a part of layered coil having no connecting part at all a little to the coil inner diameter side is wound up in the inverse direction to the other layered coil. Otherwise, a superconducting wire is wound up in the same direction to be connected so that a part of the layered coil may be fed with a current in the inverse direction. Besides, a dummy coil and a cylinder are provided inside the coil 1. Furthermore, an aluminum and a copper cylinder having excellent thermal conductivity are provided in outer peripheral side of the superconducting coil 1.