There are provided a thin transformer capable of being used in a thin display device such as a liquid crystal display (LCD) device, a light emitting diode (LED) device, and a flat panel display device including the thin transformer. The transformer includes a bobbin part including inner and outer bobbins each including a pipe shaped body part having a though-hole formed in an inner portion thereof and a flange part protruding outwardly from both ends of the body part; coils respectively wound around the inner and outer bobbins; and a core electromagnetically coupled to the coils to thereby form a magnetic path, wherein the outer bobbin includes a support part formed at the flange part formed at an upper end of the body part of the outer bobbin so as to cover a portion of the through-hole, and the inner bobbin is coupled to the outer bobbin while having one end supported by the support part.