To provide an internal combustion engine governor which controls the quantity of fuel supplied to an engine to regulate the engine speed with no use of an electric actuator.

An accumulator 20 is provided for accumulating the positive pressure in a crankcase 3 of an internal combustion engine 1 into its accumulator chamber 20A to produce displacement on its output shaft 20h corresponding to the pressure thus accumulated. The output shaft 20h of the accumulator is connected to a piston valve 17b of a carburetor. A solenoid valve 22 is provided to regulate the pressure in the accumulator chamber 20A. The control of the solenoid valve 22 regulates the displacement of the output shaft 20h to control the flow rate of a mixture to be supplied to the engine 1.