Insulated electric wire

An insulated electric wire comprising:

• a conductor formed of a plurality of element wires twisted together;
• and an insulating layer covering an outer periphery of the conductor, wherein,
• the insulating layer is formed of a thermally crosslinked product of a polymer composition and a flame retardant,
• the polymer composition contains, as a main component, an ethylene-based copolymer, polyethylene, or a combination of the ethylene-based copolymer and the polyethylene,
• the insulating layer has a gel fraction of 60% or more,
• the insulating layer has a tensile elongation of 150% or more,
• the insulating layer has a tensile elongation of 50% or more after being maintained at 150° C. for 1,500 hours,
• the insulating layer has a creep modulus of 0.3 MPa or more, as calculated under a condition of maintaining the insulating layer at 150° C. for 1,500 hours, and
• the flame retardant includes at least a bromine-based flame retardant,
• wherein the insulating layer is formed as a single, homogeneous layer.