A control apparatus for an internal combustion engine for controlling the engine while compensating for a deviation of an intake air amount from the proper value, caused by the thermal expansion and contraction of a variable intake mechanism thereof, which makes it possible to improve the control accuracy, make the engine compact in size, increase the degree of freedom of design, and reduce manufacturing costs. An ECU of an control apparatus of the engine calculates an FF correction value based on a thermodynamic model of a variable valve lift mechanism, calculates an FB correction value according to an air-fuel ratio correction coefficient and an actual air-fuel ratio, calculates a lift correction value as the difference between the FF correction value and the FB correction value or as a value of the FF correction value, corrects the valve lift by the lift correction value to thereby calculate a corrected valve lift, and carries out air-fuel ratio control and ignition timing control according to the corrected valve lift.