<p>An electrolyzed water producing device (1) comprises: a reverse osmosis filtration unit (11) having a reverse osmosis membrane (11a) for separating between treated water and concentrated water; and an electrolysis tank (12) having at least one pair of negative electrode (12b) and positive electrode (12d) and introducing thereinto only the treated water among the treated water and the concentrated water and producing electrolyzed water. The electrolyzed water producing device (1) further comprises: an introducing path (P3) for introducing the treated water into the electrolysis tank (12); and a discharging path (P9) for discharging alkali ion water produced in the electrolysis tank (12). A return flow path (P11) coupled to the introducing path (P3) is also provided and at least part of the electrolyzed water obtained in the electrolysis tank (12) is returned through the return flow path (P11) to the introducing path (P3) by a return-flow means (18).</p>
