The present disclosure relates to a heat pump system. The heat pump system removes heat generated during the generation of electric energy using a power generator and also performs heating using waste heat. Since an additional heat source is created in order to meet a heating requirement, heating control is effectively achieved, and electric power is produced so as to meet the demand of electric energy. When the power generator is likely to be over-cooled in the cold season, cooling of the power generator is stably performed by controlling the temperature and the flow rate of a cooling medium moving to the power generator.