An epoxy resin composition comprising(A) at least one epoxy resin comprising (a) a naphthalene ring-containing epoxy resin having at least one substituted or unsubstituted naphthalene ring in a molecule and having an epoxy equivalent of 175 to 210,(B) a phenolic resin having at least one substituted or unsubstituted naphthalene ring in a molecule, and(C) an inorganic filler,the substituted or unsubstituted naphthalene ring of the epoxy resin (a) being contained in an amount of 45 to 60% by weight in the total amount of the epoxy resin (A) is best suited for semiconductor encapsulation because it has good flow, a low coefficient of linear expansion, a high Tg, minimal moisture absorption, and crack resistance upon lead-free soldering.