PURPOSE: To provide a highly efficient cogenerating system by effectively utilizing a region where heat can not be utilized directly for power generation.

CONSTITUTION: The cogeneration system comprises an open cycle MHD generator 12 which is fed with high temperature gas from a burner 11, a high temperature heat exchanger 2 for heating rare gases with combustion gas discharged from the open cycle MHD generator 12, and a closed cycle MHD generator 4 which is fed with rare gases heated through the high temperature heat exchanger 2. In the cogeneration system, a region where heat can not be utilized directly is compensated for by means of both MHD generators 4, 12.