To solve such a problem of an apparatus for producing drinking water that high-purity alkaline ionized water can not be produced from reverse osmosis membrane-permeated water while saving the power and installation space of this apparatus if an auxiliary agent or the like is added to the reverse osmosis membrane-permeated water since the reverse osmosis membrane-permeated water has a small amount of mineral content and consequently it is necessary to make good the shortage of a counter ion and impress high voltage.

The apparatus for producing drinking water is characterized in that the concentrated water concentrated by a reverse osmosis membrane is electrolyzed and then the alkaline water produced by electrolyzing the concentrated water is mixed with the reverse osmosis membrane-permeated water so that high-purity alkaline ionized water can be supplied while saving the power and installation space of this apparatus.