A halogen-free resin composition for a covered wire and a wiring harness which has a base resin composition of 100 weight division having 45 to 65% by weight of a polypropylene resin, 15 to 30% by weight of a low-density polyethylene resin, 15 to 30% by weight of a styrene thermoplastic elastomer, and a metal hydrate of 80-120 weight division. The styrene thermoplastic elastomer of the composition is an aromatic vinyl-conjugated diene system block copolymer and with a peak temperature of dynamic factor (tan .delta.) thereof measured in a range from -100 to 50.degree. C. by a dynamic viscoelasticity measurement device being made in 0-30.degree. C.