To provide a cogeneration system where deterioration of energy saving property accompanying a heat excess state can appropriately be controlled by appropriately dropping output of the cogeneration system at time when the heat excess state is predicted or time when the heat excess state is caused.

The system is provided with an excess power derivation means operating or measuring excess power with respect to power load of generated power of the cogeneration system. An operation control means performs a following response state drop operation as an output drop operation for dropping output of the cogeneration system at time when occurrence of the heat excess state is predicted if power main operation control is assumed to be performed on predicted power load or heat excess management time being time when the heat excess state is caused. In the response state drop operation, a response state R where setting output is made to follow power load Eo is set to a low side and the response state R is adjusted based on excess power Eo operated or measured by the excess power derivation means.

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