There is provided a thin transformer capable of being used in a thin display device such as a liquid crystal display (LCD) device and a light emitting diode (LED) display device. The transformer includes: a bobbin part including a plurality of bobbins, each including a pipe shaped body part having a though-hole formed in an inner portion thereof, a flange part vertically protruding outwardly from both ends of the body part, and a terminal connection part protruding from one side of a lower flange part formed at a lower end of the body part and having external connection terminals connected thereto; a core inserted into the through-hole of the bobbin to thereby form a magnetic path; and a coil part including coils each wound around the plurality of bobbins, wherein the bobbin part includes an outer bobbin and an inner bobbin inserted into the through-hole of the outer bobbin to thereby be coupled thereto, and the terminal connection part of the inner bobbin protrudes in an outer diameter direction thereof.