A flame-retardant composition comprises a polyphenylene ether resin having a number average molecular weight in terms of polystyrene of 500 to 5,000 and a phosphazene compound, the content of the polyphenylene ether being 20 to 95% by weight and that of the phosphazene compound being 80 to 5% by weight. The flame-retardant composition is excellent in processability when added to resins, and can provide a resin composition that contains no halogens and has an excellent balance of processability, heat resistance and flame retardancy.