An epoxy resin composition comprising:(A) as a resin chief material a bisphenol A type epoxy resin having the following formula (1), ##STR1## wherein n is 0 to 10, R.sup.1 and R.sup.2 each represents a glycidyl group, and A.sup.1 to A.sup.8 each represents a hydrogen atom or a bromine atom;(B) as an epoxy resin curing agent,(b1) a bisphenol A or a brominated product thereof having formula (1) (wherein n is 0, R.sup.1 and R.sup.2 each represents a hydrogen atom, and A.sup.1 to A.sup.4 each represents a hydrogen atom or a bromine atom), or(b2) a novolac resin of a bisphenol A or a brominated product thereof that is obtained by linking two or more molecules of a bisphenol A or a brominated product thereof having formula (1) (wherein n is 0, R.sup.1 and R.sup.2 each represents a hydrogen atom, and A.sup.1 to A.sup.4 each represents a hydrogen atom or a bromine atom), through a methylene group(s) at any of A.sup.1 to A.sup.4 ; and(C) as an additive, a polymeric polyhydroxypolyether represented formula (1) (wherein n is 10 to 1,000, R.sup.1 and R.sup.2 each represents an alkyl group or hydroxylated alkyl group, and A.sup.1 to A.sup.8 each represents a hydrogen atom or a bromine atom).