Insulated electric wire and wiring harness

An insulated electric wire, comprising:

• a conductor comprising a plurality of elemental wires twisted together;
• and
• an insulation coating covering an outer periphery of the conductor, wherein
• the insulated electric wire includes both a flat portion and a low-flatness portion concurrently along an axial direction of the insulated electric wire, where the plurality of elemental wires and the insulation coating are each continuous through these portions;
• the conductor has, in a cross-section perpendicular to the axial direction, a flat outer shape in the flat part and a less flat outer shape in the low-flatness portion than in the flat portion in the insulated electric wire;
• in the cross-sections of the conductor for both of the flat and the low-flatness portions, deformation ratios of the elemental wires at width-directional end parts, which correspond to regions facing an outer periphery of the conductor at both ends in a width direction, are lower than the deformation ratios of the elemental wires at center parts of the conductor.