An epoxy resin composition comprising (A) a naphthalene type epoxy resin in which 35-85 parts by weight of 1,1-bis(2-glycidyloxy-1-naphthyl)alkane and 1-35 parts by weight of 1,1-bis(2,7-diglycidyloxy-1-naphthyl)alkane are included per 100 parts by weight of the resin, (B) a curing agent in the form of a naphthalene type phenolic resin, (C) an inorganic filler, and (D) a phosphazene compound 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.