The present invention provides an ozone generator comprising an anode and a cathode provided on each side of a fluororesin type cation exchange membrane, the anode being a conductive diamond electrode having conductive diamond on the surface, wherein water is supplied to an anode compartment, DC current is supplied between the anode and the cathode to electrolyze water to evolve ozone from the anode compartment and hydrogen from a cathode compartment, the conductive diamond electrode comprising a substrate having a plurality of convexo-concave and a conductive diamond film coated on the surface of the substrate is applied as the conductive diamond electrode, and a close packed layer of ion exchange resin particles or the fluororesin type cation exchange membrane with notch is closely adhered to the surface of the anode side of the fluororesin type cation exchange membrane.