To provide a composition for a wire coating member containing a non-crosslinked material at a low cost, which has superior flame retardancy, and is excellent in heat resistance, wear resistance and flexibility, and to provide an insulated wire and a wiring harness containing the composition. The composition contains (A) polypropylene, (B) a polyolefin elastomer, (C) a bromine flame retardant, (D) an antimony trioxide, (E) magnesium hydroxide, either one of (F) (F1) a zinc sulfide and (F2) a zinc oxide and (F3) mercaptobenzimidazole, and (G) a hindered phenolic antioxidant. The insulated wire includes a conductor and an insulation coat made from the composition, wherein the insulation coat has a thickness of 0.5 mm or less, and the insulated wire has an external diameter of 4 mm or less. The wiring harness includes the insulated wire.