A controller for an internal combustion engine has a hydraulic valve characteristic changing mechanism for changing valve operating characteristics of suction and exhaust valves; a valve system provided with a hydraulic valve phase variable mechanism that changes the phase; a map that stores a fuel injection quantity and an ignition timing in response to the valve operating characteristics; and delay time setting means for setting a delay time required to complete changeover of the valve operating characteristics, based on operating oil properties detected from behavior of a valve phase variable mechanism, to change the map after the delay time has elapsed. Thus, a valve operating characteristic changing timing coincides with a map changing timing to thereby achieve an improved performance of the internal combustion engine.