Method for manufacturing electric wire, electric wire, and wire harness

A method for manufacturing an electric wire in which an insulation coating is provided on the outer periphery of a conductor is provided with: a step for readying a conductor material wire that has been subjected to a solution treatment; a step for forming an insulation coating on the outer periphery of the conductor material wire and producing a coated wire; and a step for ageing the coated wire and manufacturing an electric wire.