There is provided an electrolysis device configured to use unpurified water containing a small amount of ions of alkaline earth metal such as Ca and Mg as raw water, and to have a structure of supplying the raw water to a cathode chamber in which deposition of scale of the alkaline earth metal on the surface of a cathode provided in the cathode chamber can be prevented. The electrolysis device and the apparatus for producing electrolyzed ozone water are configured by an electrolysis cell formed in a manner that a membrane-electrode assembly is configured by a solid polymer electrolyte separation membrane formed by a cation exchange membrane, and an anode and a cathode which are respectively adhered to both surfaces of the solid polymer electrolyte separation membrane, and the membrane-electrode assembly is compressed from both surfaces thereof, and thus the solid polymer electrolyte separation membrane, the anode, and the cathode are adhered to each other. A porous conductive metallic material having flexibility and having multiple fine voids therein is used as the cathode, and scale which is mainly formed of hydroxide of alkaline earth metal is stored in fine voids in the cathode, and thus localized deposition of hydroxide of the alkaline earth metal at a contact interface between the cathode and the solid polymer electrolyte separation membrane is prevented.