An epoxy resin composition for semiconductor encapsulation comprising (A) an epoxy resin, (B) a phenolic resin, and (C) butadiene rubber particles having an average particle size of secondary particles of 100 m or smaller and having such a size distribution that the proportion of secondary particles having a particle size of 250 m or smaller is 97% by weight or more, and the proportion of secondary particles having a particle size of 150 m or smaller is 80% by weight or more. Component (C) is uniformly dispersed in the composition without forming coarse agglomerates to secure low stress properties.