A conductive layer is made of a carbon fiber. A conductive lead wire is connected to the conductive layer to lead an electric signal. A conductive gel layer is attached to a first face of the conductive layer and adapted to be adhered on a living body. The conductive gel layer is formed from at least water, polymeric monomer, aminoalcohol as a pH adjuster, and a cross-linking agent so as to have a pH in a range from 8 to 13.