PURPOSE: To always optimize and stabilize electrolytic ionized-water by keeping electrolytic capacity constant to variation in feeding rate and water quality at the time of feeding water.

CONSTITUTION: By electrifying through a power circuit at the time of feeding water to an electrolyzer, electrolysis is performed to take in ionized-water. At this time, by operating a range changeover switch 28, DC voltage of the power circuit is controlled by a control unit 40 and a switching regulator 16 to produce electrolytic voltage according to the operation of the range changeover switch 28, permitting electrolysis with the electrolytic intensity of the electrolytic voltage to be performed. On this electrolysis, if feeding rate and water temp. are changed, the pulse width of the switching regulator 16 is corrected and further the electrolytic intensity is automatically controlled according to the changing condition to control the electrolytic capacity of the electrolyzer so that it may be always kept constant.