To solve the following problem: power-saving and space-saving alkaline ion water generation cannot be carried out without addition of an auxiliary etc., because of insufficient counter ion and high impressed voltage due to small amount of minerals in the permeate, despite of the desire that alkaline ion water generated from the permeate of a reverse osmosis membrane for generating high purity alkaline ion water.

The concentrate of the reverse osmosis membrane is electrolyzed, and then mixed with the permeate passing through the reverse osmosis membrane, which enables power-saving and space-saving high purity alkaline ion water supply.