Cogeneration apparatus

A cogeneration apparatus having an engine (16) and an air-cleaning device (45) provided to the engine is disclosed. The air-cleaning device (45) is provided with an air filter (66) and a hollow resonator (68). The air filter is provided at a position where a space within an air-cleaning case (61) splits into an upstream space (76) and a downstream space (77), and the resonator is provided to the downstream space and positioned at a predetermined interval with respect to the air-cleaning case. Air is introduced through the downstream space to an internal space (69) of the resonator