To provide a method for forming electrolytic water which is improved so that imperfectly electrolyzed water remaining in an electrolytic tank and electrolytic water remaining in the middle of a water supply passage are not mixed into the other electrolytic water, even if the change of electrolytic polarities is performed during electrolysis, and to provide an apparatus therefor.

Disclosed is the method for forming electrolytic water, in which after the change in the polarities of applied voltage, in a state where the supply of the water to be electrolyzed to an electrolytic tank 10 is stopped, imperfectly electrolyzed water remaining in the respective electrolytic chambers 10A, 10B of the electrolytic tank and not been sufficiently electrolyzed is subjected to electrolysis till its water quality reaches the one required by the changed applied voltage, thereafter, by supplying water from the respective electrolytic chambers to the respective water supply passages 11A, 11B, even if the change of the electrolytic polarities is performed during the electrolysis for a scale countermeasure, the imperfectly electrolyzed water remaining in the electrolytic tank and the electrolytic water remaining in the middle of the water supply passages are not mixed into the other electrolytic water. The device therefor is also disclosed.