PURPOSE: To provide the titled composition having remarkably improved flame retardancy and resistant to yellowing with sun light, by compounding a polyester elastomer with a specific halogen-containing cyanuric acid ester compound in high compatibility.

CONSTITUTION: The objective composition is obtained by compounding (A) 100pts.wt. of a polyester elastomer having an aromatic polyester segment and an aliphatic polyether segment and/or polylactone segment, with (B) 5W40pts.wt., preferably 8W30pts.wt. of a cyanuric acid-based flame retardant such as halogenated bisphenol. The flame retardant is a compound obtained by the reaction of a cyanuric halide, preferably cyanuric chloride with a halogenated bisphenol, and having preferably 1W20 triazine rings. The composition is preferably compounded further with 0.5W5pts.wt. of a mono-or difunctional epoxy compound.