This invention is to provide a membrane-electrode assembly, an electrolytic cell using the same, a method and an apparatus for producing ozone water, a method for disinfection and a method for wastewater or waste fluid treatment, by using which electrolysis reaction products or decomposition products obtained at the anode are produced at a high efficiency; channel pressure drop is minimized; and the apparatus is designed in compact size without sacrificing the production capacity.This invention relates to a membrane-electrode assembly comprising a solid polymer electrolyte membrane having a cation exchange membrane, an anode and a cathode tightly adhered to the respective surfaces of the solid polymer electrolyte membrane, with a plurality of through-holes with 0.1 mm or more in diameter over the entire surfaces of the anode, the solid polymer electrolyte membrane and the cathode, passing through these elements; an electrolytic cell using the membrane-electrode assembly; a method and an apparatus for producing ozone water; a method for disinfection; and a method for wastewater or waste fluid treatment.