JP-B-57-42157 (Patent Document 9) discloses a bipolar separator comprising a thermosetting resin such as epoxy resin, and an electroconductive substance such as graphite, and JP-A-1-311570 (Patent Document 10) discloses a separator obtained by blending an expanded graphite and a carbon black with a thermosetting resin such as phenol resin and furan resin.