The disclosure describes an epoxy resin composition and a transformer including the same. The epoxy resin composition according to an embodiment of the present invention includes an epoxy resin havinga glycol-based functional group in a main chain, a filler, a curing agent, and an imidazole-based catalyst, and the transformer according to an embodiment includes an insulated conductor wound in multiple layers in a vertical direction; a semi-conductive layer which is provided on the insulated conductor and disperses a concentrated electric field; and an insulator which is casted on the insulated conductor and the semi-conductive layer and forms an outer shape of the transformer, and the insulator consists of the epoxy resin composition including the epoxy resin having the glycol-based functional group in the main chain, the filler, the curing agent, and the imidazole-based catalyst.