To provide a control device of an engine with a PTO device enabling the widespread idling up certainly and inexpensively.

A mixer (12) which is connected to an engine (2) running on gas to generate and feed the gas/air mixture to the engine is provided with a first actuator (140) and a second actuator (150) to rotate a throttle valve via a lever member (160) so as to make the rotational speed of the engine be a first idling-up rotational speed higher than the idling-up rotational speed or the higher second idling-up rotational speed. At operating the PTO device, a control device (48) to output a signal for the mixer is provided with a switching control device (50) to operate by switching the first actuator and the second actuator.