A flame-retardant resin composition comprises 25 to 150 parts by weight of (B) a thermoplastic polyester1 elastomer, 5 to 40 parts by weight of (C) a phosphinic acid compound comprising a salt of at least one member selected from the group consisting of a phosphinic acid, a diphosphinic acid, and a polymerized product thereof, and 0.5 to 20 parts by weight of (D) an epoxy compound, relative to 100 parts by weight of (A) a polybutylene terephthalate-series resin. Such a flame-retardant resin composition is useful for various molded products and for covering the surface of an electric wire, or the like. The present invention provides a halogen-free flame-retardant resin composition which has a high heat resistance and a high flame retardancy and is excellent in hydrolysis resistance, abrasion resistance, and moldability (e.g., extrusion properties).