To provide a method for operation of an engine generator capable of effectively supplying power when a plurality of machines with different outputs are connected to one engine generator.

The start of the machine with large output is carried out with the power supply to the machine with small output stopped, when a plurality of machines supplied with power from the engine generator are provided and the outputs of the plurality of machines are different, in the method of operating the engine generator when the power which is driving source of the machine switching the start or stop according to the determination result based on the condition set in advance is supplied from the engine generator generating power by driving the generator by the engine.