A cogeneration apparatus having a ventilation-introducing channel communicating an electrical-equipment compartment with a ventilation fan is disclosed. Driving the ventilation fan causes air to be led from an exterior of a cogeneration case through the electrical-equipment compartment to the interior of the ventilation-introducing channel. The air led to the interior of the ventilation-introducing channel is led to an electrical generator. The air led to the electrical generator is exhausted through a power-generation compartment to the exterior of the cogeneration case.