Provided are a transformer, capable of simplifying a manufacturing process and enhancing heat dissipation characteristics and insulating characteristics by adopting a dual-bobbin structure and configuring a secondary winding as a metallic plate extending to the outside, and an electronic device including the same. Heat dissipation from a primary winding is facilitated by forming a primary winding at the outer side. Furthermore, a secondary metallic plate, although formed inside, includes extension portions to thereby facilitate heat dissipation from the secondary metallic plate. Also, by adopting a dual bobbin structure for outer and inner bobbins, a sufficient distance for insulation between the primary winding and the secondary metallic plate is ensured to thereby enhance an insulating function. Further, a manufacturing process can be simplified by forming a secondary winding as a metallic plate manufactured in advance.