PURPOSE: To enhance cooling capability without lowering hardness by a construction wherein, when winding a superconductor in a laminated fashion to form a coil, a width of an insulating spacer in the lengthwise direction of the conductor, the spacer being provided in an interlayer gap of the coil, is made wider than that of the gap in the lengthwise direction, and the spacer is formed with a cut hole and a groove for discharging evaporated air bubbles of coolant.

CONSTITUTION: At the time of winding a superconductor 4 into a coil, insulating spacers 6 are disposed allowing the conductor layers to have a proper insulating distance therebetween and to hold cooling gaps 5 optimum for the superconductor 4. At this time, a width of each spacer 6 in the lengthwise direction of the conductor is made wider than that of each gap 5 in the lengthwise direction of the conductor and, in case of a lack in the cooling surface area of the conductor 4, a cut hole 7 and a groove 8 for discharging evaporated air bubbles of coolant are formed in the spacer 6. By so doing, it becomes possible to allow the evaporated air bubbles of coolant such as helium to smoothly rise up in the axial direction of the coil, and to constitute spacers without reduction in its hardness.