A high-purity water producing equipment comprises a primary purification treatment system, a primary deionized water tank, a secondary purification treatment system for producing high-purity water from a primary deionized water, a circulatory system pipe for returning the produced high-purity water to a primary deionized water tank and a branch water feed system branched off from the circulatory system for feeding the high-purity water to a use point. An electrolytic unit for producing the anolyte EIW (electrolytic ionized water) to be catholyte EIW from the electrolysis of the high-purity water is provided as a bypass midway along the circulatory system. The anolyte EIW is added to the circulatory pipe downstream of the branching point toward the use point, when cleaning of units is necessary.