A fuel supply control method for internal combustion engines, which is capable of stabilizing the engine rotational speed to a desired idling speed immediately after the rotational speed of the engine at idle suddenly changes due to an external disturbance such as a change in the electrical load on the engine. The fuel quantity to be supplied to the engine is determined in accordance with operating conditions of the engine in the idling condition, and the determined fuel quantity is corrected by a correction value which is determined in response to the difference between a desired idling speed of the rotational speed of the engine and an actual value thereof. When the absolute value of a detected rate of change in the rotational speed of the engine is larger than a predetermined value, the correction value is corrected to thereby correct the determined fuel quantity.