PROBLEM TO BE SOLVED: To provide an apparatus for adding metal ion-containing acidic water capable of restraining an oxide film from being formed on the surface of a metal member, and a water use instrument.SOLUTION: The apparatus for adding metal ion-containing acidic water includes: an acidic water generation unit for generating acidic water a metal ion-containing water generation unit which has a housing part, where the metal member is housed, and in which the acidic water generated from the acidic water generation unit is treated with the metal member to generate metal ion-containing acidic water and an addition unit for adding the metal ion-containing acidic water generated by the metal ion-containing water generation unit to an object. The apparatus for adding metal ion-containing acidic water is constituted so that water, which has the pH higher than that of the metal ion-containing water generated by the metal ion-containing water generation unit, is introduced into the housing part to immerse the metal member in the introduced water.
