To provide an underground heat storage type cogeneration system capable of preventing waste use of heat by seasons found in a conventional cogeneration system, simultaneously preventing the depletion of underground heat source of an underground heat source heat pump, supplying stable heating for a long period, and reducing CO2 emissions in a cold region.

This underground heat storage type cogeneration system comprises an underground heat source heat pump system 10 composed of a cogeneration system 1 driven by a driving source and including a power generator capable of simultaneously outputting electric energy and exhaust heat energy, an underground heat exchanger 12, and the heat pump 13, for storing the heat in the ground.