In an internal combustion engine employing a variable lift and working angle control mechanism (1) and a variable phase control mechanism (21), a first sensor (14) is provided to detect an actual control state of the variable lift and working angle control mechanism every sampling time intervals. Also provided is a second sensor (16) that detects an actual control state of the variable phase control mechanism every sampling time intervals. At least one of the sampling time interval for the first sensor and the sampling time interval for the second sensor has a characteristic that the one sampling time interval varies relative to the engine speed. A rate of change in the sampling time interval for the first sensor with respect to the engine speed is different from a rate of change in the sampling time interval for the second sensor with respect to the engine speed.