A method for deciding the combustion state of each cylinder on the basis of an ion current signal generated between gaps of an ignition plug in an internal combustion engine, and a fuel control system which reduces a fuel injection quantity while suppressing the combustion change of each cylinder and reduces a non-combustion composition in an engine exhaust gas after starting of engine. The fuel control system for an internal combustion engine comprises: cylinder-individual fuel injection quantity correcting means 45, 46 for correcting the fuel quantity injecting quantity in each cylinder so that the sum of fuel injection quantities to be supplied to the cylinders of the internal combustion engine having a plurality of cylinders decreases in each combustion cycle of each said cylinder and a difference between the combustion state value of the first cylinder of the internal combustion engine and that of the second cylinder thereof decreases; and fuel injecting means 20 for injecting into each cylinder the fuel injection quantity for each cylinder of said internal combustion engine corrected by said fuel injection quantity correcting means for each cylinder.