A separator for solid polymer-type fuel cell is produced by molding the resin composition which comprises an electroconductive agent and a radical-polymerizable thermosetting resin system by a resin molding method. The electroconductive agent comprises a carbon powder. The radical-polymerizable thermosetting resin system may comprise a radical-polymerizable resin (especially, a vinyl ester-series resin) and a radical-polymerizable diluent. It is preferred that the double bond equivalent of the radical-polymerizable resin may about 200 to 1,000 and that the hardened radical-polymerizable thermosetting resin system has a glass transition temperature of 120.degree. C. or more. The weight ratio of the electroconductive agent to the radical-polymerizable thermosetting resin system may be about 55/45 to 95/5. Such a separator is suitable for fuel cell (in particular, solid polymer-type fuel cell), and can be produced with advantageous for commercial production.