An epoxy resin composition comprising: (A) an epoxy resin having at least three epoxy groups per molecule and an epoxy equivalent of 170 or lower; (B) an epoxy resin having a phenolic nucleus and two epoxy groups in such an amount that a weight ratio of the epoxy resin (B) to the epoxy resin (A) ranges from 35/65 to 65/35; (C) a phenolic curing agent in such an amount that a molar ratio of phenolic hydroxyl groups to the whole epoxy groups in the composition ranges from 0.5 to 1.5; and (D) an inorganic filler in an amount of from 86 to 92 wt %, based on a total weight of the composition. The composition provides encapsulated semiconductor devices much less warped than those encapsulated with a conventional composition.