Fuel injection control of an internal combustion engine requires an optimized fuel amount that can be burned completely with oxygen in intake air to be supplied, but the oxygen concentration in the atmospheric air is affected by humidity.By separately calculating a dry air flow rate that directly affects the oxygen amount and a humidity flow rate that is a change factor of the oxygen concentration in the intake air of the internal combustion engine, the fuel can be supplied to the cylinder of the internal combustion engine at an optimized air-fuel ratio. In addition, highly precise control involving EGR for flowback of a part of the exhaust gas flowing in the exhaust pipe to the intake pipe can also be achieved.