There is provided an apparatus for manufacturing sterilizing water, in which the sterilization power of a chlorine-based solution consisting of sodium hypochlorite or chlorine dioxide or a mixture thereof is fully achieved while the generation of chlorine gas is restrained, and desired sterilizing water is manufactured by properly feeding and mixing three liquids of water, an acid solution, and a chlorine-based solution at a fully controlled concentration. In the apparatus for manufacturing sterilizing water of some aspect of the present invention, after both acid solution and chlorine-based solution have been diluted with raw water in a feeder, the dilute solutions can be mixed with each other by a mixer.