A process of producing a conducting material suitable for being filled in TSVs for LSI chip 3D package, etc. includes that a solution containing a monomer that provides a conducting polymer, anions, and metal ions such as Ag+ or Cu2+ is irradiated with ultraviolet radiation or light having the energy necessary for exciting electrons up to an energy level capable of reducing the metal ions to precipitate a conducting polymer/metal composite. This enables an electrical conductor of high electrical conductivity to be precipitated faster than could be achieved by conventional processes.