NOVELTY - A resin composition comprises an epoxy resin, a hardening agent, a hardening accelerator, and a carbon material. 5-100 Mass% of the carbon material is high-crystalline artificial graphite having an average particle diameter of 100-150 mu m. The hardening accelerator is a phosphorus compound having a molecular weight of 300-1000, salt of diazabicyclo compound and organic acid, urea derivative, imidazole compound having a molecular weight of 100 or more, and/or tertiary amine compound having a molecular weight of 120-1000.    USE - Resin composition is used for injection-molding separators (claimed) of fuel cells.    ADVANTAGE - The resin composition provides fuel-cell separators having excellent electroconductivity, contains less impurities, has excellent heat stability, fluidity, electroconductivity, and dimensional accuracy, and does not cause deterioration in performance of a solid electrolyte. The resin composition provides separators which form highly efficient fuel cells.    DETAILED DESCRIPTION - A resin composition comprises an epoxy resin, a hardening agent, a hardening accelerator (0.1-20 weight parts with respect to 100 weight parts of hardening agent), and a carbon material (50-85 mass%). 5-100 Mass% of the carbon material is high-crystalline artificial graphite having an average particle diameter of 100-150 mu m. The hardening accelerator is a phosphorus compound having a molecular weight of 300-1000, of formula: P(-R1)(-R3)(-R2) or R4-P+(-R1)(-R3)-R2.X-, salt of diazabicyclo compound and organic acid, urea derivative of formula: X'-NH-CO-NY'Z, imidazole compound having a molecular weight of 100 or more, and/or tertiary amine compound having a molecular weight of 120-1000.    R1-R4=H, alkyl, aralkyl, aryl or their derivatives;    X=substance chosen from tetracoordinated boron compound, halo, and hexacoordinated antimony compound;    X'=(un)saturated alkyl or its derivatives, or aryl or its derivatives;and    Y',Z=(un)saturated alkyl.    An INDEPENDENT CLAIM is included for manufacture of resin composition, which involves melt-kneading all the components from a temperature more than the softening temperature of epoxy resin or hardening agent, to a temperature at which hardening reaction does not advance during mixing.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of the separator.    Separator (10)    Flat portion (11)    Partition (12)    Channel (13)