An integration correction term is calculated on the basis of a deviation of an actual rotation speed with respect to a target rotation speed of an internal combustion engine when the internal combustion engine is idling and used to correct a fuel supply amount, thus controlling an idling rotation speed of the internal combustion engine. At the time of and/or immediately after initiation of the internal combustion engine, prospective correction in accordance with friction which exists at an early initiation stage of the internal combustion engine is conducted on the fuel supply amount.