Disclosed is a phase shift transformer for supplying voltage to a plurality of unit power cells in a medium voltage inverter system. The phase shift transformer according to the present invention comprises a first bushing arranged by the side of a tank and connected to a first winding to apply high voltage and a plurality of second bushings arranged on the top of a cover and connected to each of a plurality of second windings to output low voltage, wherein three outputs of the plurality of second bushings can be applied to unit power cells.