PROBLEM TO BE SOLVED: To provide an insulating resin composition for an insulated wire, capable of achieving excellent heat aging resistance while sufficiently suppressing deterioration in dielectric characteristics in a GHz band.SOLUTION: The insulating resin composition for an insulated wire contains an olefinic resin and an antioxidant. The antioxidant is blended in an amount of 0.05-1.0 pt.mass based on 100 pts.mass of the olefinic resin. The antioxidant is composed of a primary antioxidant comprising a phenolic antioxidant having a structure different from a hindered phenol structure, and a secondary antioxidant comprising a phosphorus-based antioxidant. The blending ratio of the secondary antioxidant in the antioxidant is 10-90 mass%. The structure different from the hindered phenol structure is a semi-hindered phenol structure or a less-hindered phenol structure.SELECTED DRAWING: None
