An epoxy resin composition comprising (A) a biphenyl skeleton epoxy resin, (B) a biphenyl skeleton phenolic resin as a curing agent, (C) molybdenum compound, and (D) an inorganic filler is suited for semiconductor encapsulation since it is effectively moldable and cures into a part having improved reflow crack resistance, moisture resistance, and flame retardance. It does not pose a hazard to human health or the environment.