A cogeneration system including an engine, which drives a generator to generate electricity, a cooling/heating unit using a heat pump type refrigerant cycle, in which a refrigerant is circulated through at least one compressor, a four-way valve, a first outdoor heat exchanger, a first expansion device, and an indoor heat exchanger, in this order, during a cooling operation of the cogeneration system, and a waste heat consuming heating unit using a refrigerant cycle, in which the refrigerant is circulated through the compressor, the four-way valve, the indoor heat exchanger, a second expansion device, and a second outdoor heat exchanger to be heated by waste heat of the engine, in this order, during a heating operation of the cogeneration system. In accordance with the cogeneration system, it is possible to maximize utilization of engine waste heat during the heating operation and to achieve an enhancement in heating performance.