PURPOSE: To provide an air governor device for an industrial vehicle engine which is improved for utilizing the maximum ability (output) of the engine as required.

CONSTITUTION: A cylinder chamber 21 which movably houses a stabilizer piston 22 for opening and closing a governor valve 13 is composed of one chamber 21a communicated with an air-fuel mixture supplying passage 12a, and the other chamber 21b to which an atmospheric pressure or a negative pressure of an intake manifold 11 are applied while being selectively switched through a solenoid vacuum valve 26. When an accelerating pedal is maximumly operated in order to obtain a high output, a negative pressure is applied to the chamber 21b and operation of the stabilizer piston 22 is temporarily stopped until an engine speed reaches a preset valve. Thus, the governor valve 13 is kept in a total open position which is set by a spring, a supplying amount of air-fuel mixture is increased, so as to obtain a high output. When the engine speed reaches the preset value, an atmospheric pressure is applied to the chamber 21b, and the operation of the stabilizer piston 22 is restarted.