NOVELTY - Operating method of electrolysis device involves supplying voltage to anode (12) and cathode (14), and operating with hydrogen generation potential at cathode of -0.2 V to -0.7 V based on reversible hydrogen electrode (RHE) potential when electrolyte is acidic, or hydrogen generation potential at the cathode of -0.2 V to -0.9 V based on RHE potential when the electrolyte is neutral or alkaline.    USE - Operating method of electrolysis device (claimed). Uses include but are not limited to dehumidifying device, oxygen concentration device, deoxygenation device, salt electrolysis device, gas sensor and humidity sensor.    ADVANTAGE - The method is carried out efficiently and precisely.    DETAILED DESCRIPTION - Operating method of electrolysis device involves supplying voltage to the anode and the cathode, and operating with a hydrogen generation potential at the cathode of -0.2 V to -0.7 V based on reversible hydrogen electrode (RHE) potential when the electrolyte is acidic or hydrogen generation potential at the cathode of -0.2 V to -0.9 V based on RHE potential when the electrolyte is neutral or alkaline, and oxygen reduction initiation potential at cathode of 0.88 V to 0.75 V based on RHE potential when the electrolyte is acidic or oxygen reduction initiation potential at the cathode is 0.94V to 0.87 V based on RHE when the electrolyte is neutral or alkaline. The electrolyte is acidic, neutral, or alkaline. The electrolysis device comprises an anode, a cathode having a nitrogen-containing carbon alloy catalyst, and an electrolytic cell having a membrane electrode assembly composed of an electrolyte present between the anode and the cathode. The potential at the cathode is less than hydrogen generation potential at a cathode in which platinum is used as a catalyst.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic structure of electrolysis device.    Power source (11)    Anode (12)    Ion-exchange membrane (13)    Cathode (14)    Water-supply tube (15)