The present disclosure relates to an apparatus for predicting power loss of a transformer, and more particularly, to an apparatus for predicting power loss of a transformer, which is capable of predicting power loss by comparing temperature data of the transformer with reference data thereof. An apparatus for predicting power loss of a transformer according to one embodiment of the present disclosure includes a measurement unit configured to measure a temperature of a transformer, a calculation unit configured to calculate temperature data of the transformer on the basis of the measured temperature, a storage unit configured to set and store the reference data of the transformer, and a determination unit configured to determine power loss of the transformer by comparing the temperature data with the reference data, wherein the reference data includes power loss according to the temperature data.