An engine generator for driving an air motor to energize an engine is provided which reduces an installation space and facility and running costs. The engine generator (EG) is attached to a fire extinguishing facility (14). The fire extinguishing facility is designed to eject unburnable gas supplied from gas containers (11) and comprises an air motor (10) for driving an engine, and a valve unit (12) designed to drive in response to an instruction signal, control a pressure of the unburnable gas from the gas container and supply the pressure controlled unburnable gas to the air motor (10).