An insulated wire, having at least one thermosetting resin layer and at least one thermoplastic resin layer in this order, as covering layers, on a conductor having a quadrilateral cross-section, wherein, in a coating thickness of the covering layers, in each side to be formed on 4 sides of the quadrilateral cross-section of said insulated wire, a difference between the maximum value and the minimum value is each 20 μm or less, and a value of the maximum value divided by the minimum value of the whole sides is 1.3 or more; a motor coil; and an electrical or electronic equipment.