An insulated electric cable including: two first core wires, each of the two first core wires including: a first conductor; and a first insulating layer covering the first conductor; and two second core wires, each of the two second core wires including: a second conductor having a cross-sectional area smaller than that of the first conductor; and a second insulating layer covering the second conductor; wherein the two second core wires are mutually stranded to form a subunit, and wherein one of the two first core wires, another of the two first core wires, and the subunit are mutually stranded and are in contact with each other to form a core member.