PURPOSE: To ensure uniform cooling conditions for bipolar electric current leads for superconducting coil by uniformly twisting the multiple +, - enamel- coated copper or aluminum alloy lead wires, inserting them in a pipe, and circulating helium gas in the pipe.

CONSTITUTION: Multiple +, - enamel-coated copper or aluminum alloy lead wires are twisted at a short pitch into a single unit and inserted into a pipe to form an electric current lead 5. This is divided into two poles at a low- temperature terminal 53 and electric current is supplied to a superconductive coil 1 within the liquid helium 2. Gas helium is made to flow in a direction indicated by the arrow 7 in order to cool the lead wires. As a result, it is possible to maintain uniform Joule heat generation at both poles and uniform cooling conditions and, at the same time, to balance the electromagnetic force produced by the lead wires within the electric current lead 5, preventing the generation of external electromagnetic force.