Abstract: This invention relates to a reduced water producing apparatus, which can mass-produce reduced water, wherein oxidation-reduction potential maintains for a long period successively, from not only industrial water, natural water but pure water speedily and inexpensively, and that suited for industrial mass production of reduced water. The apparatus have a water tank, at least one electrode plate unit, and a voltage impressing means for impressing high-frequency alternating voltage, wherein the electrode plate unit includes two alternating electrode plates in which alternating voltages impressed by the voltage impressing means are varied to be modulated waves of mutually opposite phases and a ground electrode plate arranged to oppose the two alternating electrode plates, and wherein surfaces of these electrode plates are formed of titanium or platinum.