In this layer, the Ti:N, Ti:C:N sublayer is formed on the etched Ti substrate, and DLC is coated, and afterwards, the proportion of the sp2 carbon structure and the sp3 carbon structure is changed to lower the surface specific resistance, and by having electrochemical traits, the trait of enhancing the adhesion of the Ti substrate and the DLC layer is caused to have high durability and electrochemical traits, providing wide-area water-treatment DLC/Ti electrode manufacture method.