A control unit for an internal combustion engine is configured for allowing smooth operation of the internal combustion engine by increasing an intake amount while maintaining an opening timing of an intake valve constant, at the time of low-rotation, high-load state. A valve opening/closing timing control apparatus includes a phase adjustment mechanism configured to vary a relative rotational phase between a driving side rotary body rotatable in synchronism with a crankshaft of the internal combustion engine and a driven side rotary body rotatable together with an intake cam shaft. After an opening timing of the intake valve, the relative rotational phase is displaced in the advancing direction.