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A smaller and thinner transformer can be realized by wrapping a first secondary winding (5) so that a gap (5a) larger than the gauge of the first secondary winding (5) is formed between adjacent wraps of the first secondary winding (5), and so that two coils (A, B) are disposed in a structure in which the wraps of a second secondary winding (10) of one coil (B) are disposed between the wraps of the first secondary winding (5) of the other coil (A).