Provided is an epoxy resin composition comprising a prescribed epoxy resin, an acid anhydride, a salt of diazabicycloundecene or diazabicyclononene and an organic compound, and a core-shell polymer. The epoxy resin composition, which has low viscosity and outstanding pot life, has a viscosity of 3000 mPa.s or less at 25 DEG C and a viscosity of 4500 mPa.s or less three hours after the start of measurement when measurement is continued for three hours at 25 DEG C, and can be used to manufacture a fiber-reinforced composite material with outstanding heat resistance and ductility.