NOVELTY - An electrolytic cell (11) includes a fluorine resin-based ion exchange membrane (4a) through which water vapor is passed to an other ion exchange membrane (4b) through a cathode (6), based on the vapor pressure difference. When a specific voltage is applied to the cathode and an anode (8), the water vapor is electrolyzed and hydrogen and oxygen are generated on cathode and anode surfaces, respectively.    USE - Used for electrolyzing water to remove oxygen and hydrogen. The oxygen is supplied to aircraft, spacecraft and oxygen burners for jewelry processing, and hydrogen is supplied to a fuel cell.    ADVANTAGE - Since water vapor is electrolyzed, water is not mixed with generated oxygen and hydrogen and need for a vapor-liquid separation tank is eliminated. The weight of electrolysis apparatus is reduced and oxygen and hydrogen of high purity are obtained.    DETAILED DESCRIPTION - An electrolytic cell includes a compartment (3) into which hot water is passed from a water tank through a water-flow inlet (2). The other compartment (7) sandwiched between the compartments (3, 10), comprises the fluorine resin-based ion-exchange membrane (4a) through which water vapor is passed to the other ion exchange membrane (4b) through the sponge-like cathode. The water vapor is electrolyzed by applying specific voltage to the cathode and anode which is plated with porous titanium and platinum. A proton is passed from the anode to the cathode through the ion exchange membrane (4b). The hydrogen and oxygen generated on cathode and anode surfaces are discharged through hydrogen and oxygen discharge ports (5,9) provided in compartments (7,10), respectively. The water in the electrolytic cell is discharged to the water tank through a water discharge port.    DESCRIPTION OF DRAWING(S) - The figure shows a structure of the water electrolysis apparatus.    water electrolysis apparatus (1)    water flow inlet (2)    compartments (3,7,10)    ion exchange membranes (4a,4b)    hydrogen discharge port (5)    cathode (6)    anode (8)    oxygen discharge port (9)    electrolytic cell (11)