PURPOSE: To increase a current made to flow into a superconducting magnetic field, by a method wherein a cathode chamber and an anode chamber are made by a bipolar membrane, a current is made to flow through, water inside the bipolar membrane is ionized into hydrogen ions and hydroxide ions sequentially and these ions are made to migrate toward the respective poles thereof.

CONSTITUTION: A cathode chamber 3 and an anode chamber 4 are made by using a bipolar membrane as a diaphragm. On the occasion, the side of the bipolar membrane 1 emitting hydrogen ions is set inside of the cathode chamber 3 and a water solution of salt or an acid is put in the chamber. As for the anode chamber 4, the side of the bipolar membrane 2 emitting hydroxide ions is set inside of this chamber and a water solution of oxyacid salt or a base is put in the chamber. By making a current flow through electrodes, a hydrogen gas is produced in the cathode chamber 3 and an oxygen gas in the anode chamber 4, while a large current is made to flow through a superconducting magnetic field 5 simultaneously by the hydroxide ions coming out of the outer face of the diaphragm of the cathode chamber 3 and by the hydrogen ions coming out of the outer face of the diaphragm of the anode chamber 4.