A cogeneration system is disclosed. The system has a cooling water circulation channel for returning cooling water of the engine to the engine after some of the cooling water has been removed. The cooling water circulation channel is provided with a cooling water pump for pressure-feeding the cooling water; electricity supplying means; and a control part for performing a control so that electrical energy is supplied from the electricity supplying means to a motor for driving the cooling water pump when a power outage signal is received.