Coil-winding method and coil unit formed by the method

A coil-winding method for forming a coil unit includes the steps of winding first and second wires substantially parallel to each other simultaneously around a first layer position of a core to form a first turn, winding the first and second wires simultaneously to form a second turn while the second wire is disposed directly around the core, the first wire of the second turn adjacent to the first turn being disposed between the first and second wires of the first turn in the first layer so as to form a second layer, and winding the first and second wires simultaneously to form a third turn while the second wire is disposed directly around the core, the first wire of the third turn being disposed in the second layer and wound between the second wire of the first turn and the second wire of the second turn in the first layer.