A cogeneration system including a heat pump type air conditioner including an outdoor heat exchanger and an outdoor heat exchanger bypass conduit, and a cogeneration unit including a second outdoor heat exchanger, an outdoor heat exchanger bypass conduit, second outdoor heat exchanger connecting conduits, and second outdoor heat exchanger bypass conduit to cause the refrigerant to be evaporated in the second outdoor heat exchanger during a heating operation of the heat pump type air conditioner, and to cause the refrigerant to be condensed in the outdoor heat exchanger during a cooling operation of the heat pump type air conditioner, so that the heat pump type air conditioner can provide a constant heating capacity irrespective of a variation in outdoor temperature during the heating operation thereof.