The present invention relates to a power generating apparatus and method for assisting an engine, capable of supplying auxiliary power to an engine transmission shaft when the engine is transmitting power to the engine transmission shaft via a gearbox. The power generating apparatus comprises: a power supply unit for providing a high voltage power source; a driver for converting the high voltage power source into a driving power source and transmitting same; and a direct-current motor for converting the driving power source transmitted by the driver into the auxiliary power to be transmitted to the engine transmission shaft; wherein the rotational speed of the direct-current motor driving the engine transmission shaft is enabled to be higher than that of the engine driving the engine transmission shaft, so as to supply the auxiliary power to the engine transmission shaft.