A cooling device for a transformer, capable of reducing heat generation from windings and a core, is provided. The cooling device for the transformer includes a primary winding and a second winding wound around a center part of the core and separated from each other. A heat-dissipating panel for releasing heat generated from the core, the primary winding, and the secondary winding to the exterior using heat conductance is inserted between the primary winding and the secondary winding. In addition, the heat-dissipating panel is configured to release heat using exposed edges of the primary winding and the secondary winding.