Abstract: Acid water containing hypochlorous acid is produced by an anode chamber of an electrolytic chamber, and alkali water is produced by a cathode chamber. The acid water is reserved in a reservoir tank and is returned into the anode chamber by actuating a return pump. The acid water returned into the anode chamber is subjected to further electrolysis, and fed in the cathode chamber through a first water supply line, an interconnection means and a second water supply line, so as to sterilize the interiors of the first water supply line, the interconnection and the second water supply line.

Abstract: Chlorine ion-containing water supplied from one of water discharge pipelines of an electrolysis vessel of an apparatus for continuously forming electrolyzed water is caused to flow backwardly to one of electrode chambers and a water supply branch pipe thereof, passed through a water supply branch pipe of the other of the electrode chambers and/or a water supply pipeline at the upstream thereof and discharged through the other of the electrode chambers and from the other of the water discharge pipe lines. In this state, water in the electrolysis vessel is electrolyzed while operating the electrode of the electrode chamber in which water is caused to flow backwardly as an anode, and the electrolysis vessel and water channels at the upstream thereof are cleaned and sterilized by electrolyzed cleaning water in which hypochlorous acid is formed.