In a co-generated power supply system for performing dispersed power supply to a load, a wind turbine generator, a solar cell and a fuel cell whose rated voltages are made equal to a rated voltage of a storage battery are used as DC power sources. These DC power sources, a commercial AC power source and the load are connected to each other via a bi-directional electronic transformer. Thus, the co-generated power supply system, in which the electric power of a natural energy system having many fluctuation factors is combined with stable electric power such as a load leveling battery or a fuel cell, allows the stable electric power to be supplied to the load via the electronic transformer commonly, thereby reducing the cost and enhancing the performance of the entire system.