Insulated wire

An insulated wire comprising a stranded wire conductor, and an insulator that covers an outer circumference of the stranded wire conductor, wherein

• the insulated wire is configured to be used in a state of being in contact with an oil composed of AT fluid or CVT fluid,
• the stranded wire conductor is made up of at least a plurality of copper-based element wires that are twisted together, and has been heat-treated after circular compression,
• the copper-based element wires have an Ni-based plated layer on a surface thereof,
• the Ni-based plated layer has been compressed by the circular compression, and
• the insulator is composed of a cross-linked ethylene-tetrafluoroethylene based copolymer and
• a heating deformation rate of the insulator is 65% or more at the time after an edge of 0.7 mm in thickness is pressed against a surface of the insulator with a Load defined by Formula 1 and is kept under an atmosphere at 220° C. for 4 hours in conformity with ISO6722, Load [N]=0.8×√{i×(2D−i)} (Formula 1)
• where, D is a finished outer diameter [mm] of the insulated wire, and i is a thickness [mm] of the insulator,
• and the heating deformation rate is obtained by Formula 2,
• Heating Deformation Rate (%)−100×(Minimum Wire Outer Diameter [mm] after subjected to Heating Deformation Outer Diameter [mm] of Stranded Wire Conductor)/(Wire Outer Diameter [mm] before being subjected to Heating Deformation−Outer Diameter [mm] of Stranded Wire Conductor) (Formula 2).