PURPOSE: To lower the internal stress of cured products while maintaining the adhesion to semiconductor chips by incorporating a specific stress-lowering agent in an epoxy resin composition comprising an epoxy resin and a curing agent.

CONSTITUTION: A silicone polymer represented by formula I (wherein R1 is H, methyl, phenyl, 2-aminoethyl or glycidyl; R2 is methyl, ethyl, n-propyl or isopropyl; m and n are each an average value of 10-200; and k is 0, 1 or 2) (e.g. formula II) is added as a stress-lowering agent to an epoxy resin composition comprising an epoxy resin (e.g. bisphenol A epoxy resin) and a curing agent (e.g. phenol novolac resin). In consequence, the cured product of the epoxy resin composition is given flexibility, and its modulus of elasticity can be reduced. Hence, the resulting epoxy resin composition may suitably be used as a sealing material for semiconductor chips.