TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Material: The electroconductive base material contains carbon raw material having electroconductivity. The electroconductive base material consists of graphite, carbon black, fullerene, carbon nanotube (CNT), vapor-phase-epitaxy carbon fiber (VGCF), carbon felt, carbon cloth, and carbon paper. The electroconductive base material and hydrophilic polymer layer are coupled by covalent bond or hydrogen bond. The electroconductive base material contains aluminum, nickel, iron, copper, gold, platinum, stainless steel, iron-silicon alloy, calcium silicon alloy, aluminum zinc-silicon alloy, molybdenum-vanadium alloy, and nickel copper alloy.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compound: The electronic mediator is oxidation-reduction substance chosen from anthraquinone derivative, naphthoquinone derivative, benzoquinone derivative, and iso alloxandine derivative. The electronic mediator is oxidation reduction substance chosen from anthraquinone carboxylic acid, aminoanthraquinone, diamino anthraquinone, anthraquinone sulfonic acid, diamino anthraquinone sulfonic acid, anthraquinone disulfonic acid, diamino anthraquinone disulfonic acid, ethyl anthraquinone, methyl naphthoquinone, methyl-amino naphthoquinone, bromo methyl-amino naphthoquinone, dimethyl naphthoquinone, dimethylamino naphthoquinone, rapa call (LpQ), hydroxy (methyl butenyl) amino naphthoquinone, naphthoquinone sulfonic acid, trimethyl amino benzoquinone, flavin mononucleotide, and their derivatives.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The electronic mediator (1-30 mol%) is introduced with respect to structural hydrophilic monomer unit of hydrophilic polymer in hydrophilic polymer layer. The electronic mediator has hydrophilic functional group. Preferred Polymer: The hydrophilic polymer is a polymer containing functional group chosen from amino group, imino group, carboxy group, and sulfonic acid group. The hydrophilic polymer is polyethylene imine, polyvinyl amine, polyallyl amine, polyacrylic acid or polymethacrylic acid.