Provided are a non-halogen flame retardant epoxy resin composition comprising (A) a silicon-containing, phosphorus-modified epoxy resin, (B) a multifunctional epoxy resin, (C) a mixed curing agent of an amine curing agent and a phenolic curing agent and (D) a metal hydrate inorganic flame retardant, and a prepreg and copper-clad laminate using the same. The epoxy resin composition in accordance with the present invention exhibits excellent flame retardancy without use of a halogen flame retardant, and also advantageously provides well-balanced various physical properties which are to be required in copper-clad laminates, such as higher heat resistance and copper peel strength, and lead heat-resistant characteristics after moisture absorption.