In a multi-layer insulated wire including: a conductor; an inner layer formed in periphery of the conductor; and an outer layer formed in periphery of the inner layer, the inner layer is made of a resin composition containing a base polymer containing polyolefin as a main component, and the outer layer is made of a resin composition containing a base polymer containing polyolefin as a main component so as to contain 80 or more and 250 or less parts by mass of metallic hydroxide per 100 parts by mass of the base polymer. The multi-layer insulated wire having an expansion start temperature of the outer layer that is equal to or lower than 344° C. is used.