The present resin composition is improved in compatibility between thermoplastic polyester and polyphenylene ether and is excellent in processability, solvent resistance, and impact strength.This resin composition comprises:100 parts by weight of a composition comprising(A) 5-95 % by weight of a polyphenylene ether resin and(B) 95-5 % by weight of a thermoplastic polyester and0-100 parts by weight based on said composition comprising (A) and (B) of a rubber-like polymer, and0.01-10 parts by weight based on said composition comprising (A) and (B), of (D) a compound comprising dinitrodiamine represented by the formula (I): ##STR1## wherein X represents a divalent chain aliphatic, cycloaliphatic or aromatic group which may contain halogen or oxygen, R.sup.1 represents a hydrogen atom, a chain aliphatic group, a cycloaliphatic group or an aromatic group and when X and R.sup.1 are both chain aliphatic groups, the nitrogen atoms may further link through R.sup.1 to each other, R.sup.2 and R.sup.3 each represents a hydrogen atom or an alkyl group of 1-12 carbon atoms and R.sup.2 and R.sup.3 may link to each other to form a ring.