A resin composition includes a polyolefin resin. A viscosity of the resin composition is within a range of not less than 500 Pa·s and not more than 2300 Pa·s under measurement conditions of a measurement temperature of 170° C. and a measurement frequency of 1 Hz. A strain hardening rate of the resin composition in uniaxial elongational viscosity measured under measurement conditions of a measurement temperature of 150° C. and a strain rate of 3.0 s−1 is not less than 800%. A foam insulated wire includes a conductor, and a foam insulation of the resin composition extruded on an outer periphery of thereof. A diameter of the conductor is 3.5 to 18 mm, and an outer diameter of the foam insulation is not less than 8 mm.