To enable an internal combustion engine to minimize resonance influence.

In a cam timing drive system of an internal combustion engine, a resonance control method minimally suppressing resonance influence is provided. A variable cam timing unit is connected to a cam shaft, and a crankshaft and the variable cam timing unit are connected, together with a cam timing drive system. The variable cam timing unit provides a cam phaser, having a variable compliance state between the cam timing drive system and the cam shaft. The cam timing drive system displays resonance state variations in a timing drive force across an engine revolution region, and timing drive force changes are different between locked and unlocked cam phasers. The resonance control method includes a process, which selects the cam phaser state at a predetermined revolution speed, in order to minimize the resonance influence during an engine running.