Abstract: A first resin is prepared which has a content of electrically conductive particles adjusted in the range from 60 wt % to 90 wt %, and a melt shear viscosity adjusted in the range from 1×103 Pa.sec to 1×107 Pa.sec. A second resin is prepared which has a content of electrically conductive particles that is adjusted in the range from 50 wt % to less than 90 wt % and that is less than that of the first resin. The second resin has a melt shear viscosity adjusted in the range from 1×102 Pa.sec to less than 1×105 Pa.sec. A resin block prepared from the first resin is placed in a mold, and the second resin is injection molded into the mold while heating the mold to the melting temperature of the first resin or above.