A separator material suitable for a polymer electrolyte fuel cell and a method of producing the same. The separator material exhibiting gas impermeability, strength, dimensional stability during long-term use, and only a small degree of dissolution of organic substances which hinder the cell reaction. The separator material includes a graphite/cured resin molded product produced by binding a graphite powder using a mixed resin prepared by mixing an epoxy resin with a specific epoxy equivalent and a phenolic resin with a specific hydroxyl equivalent at a specific equivalent ratio and adding an imidazole compound without an amino group as a curing accelerator. The graphite/cured resin molded product has, when immersed in hot water at 90.degree. C., a water absorption elongation percentage after 500 hours of immersion of a specific value or less and an amount of ammonium ions dissolved and an amount of TOC dissolved after 50 hours of immersion of specific values or less. The method of producing the separator material includes preforming a molding powder obtained by grinding a kneaded product of a mixed resin and a graphite powder to prepare a preform, and thermocompression-molding the preform in a mold.