The present invention relates to a conductive diamond electrode, comprising a substrate having a plurality of convex and concave part disposed over the entire surface of the conductive diamond electrode, and a diamond film coated on the surface of said substrate, wherein the width of each convex part of said convex and concave part is in a range from 0.2 mm to 1 mm. The present invention can provide a conductive diamond electrode, applying a thin film of conductive diamond and a thick substrate, being less expensive than a self-supported type conductive diamond electrode and also having mechanical strength enough to be used in the zero-gap electrolysis, functioning stably for a long time with smooth water supply or gas liberation, and an ozone generator using the conductive diamond electrode.