PURPOSE: To secure the optimum air/fuel ratio following a change in an intake air flow rate even at transient driving by delaying an opening/closing motion of a first opening/closing valve than a required opening/closing motion by a predetermined crank angle period and by setting a fuel injection amount based on the intake air flow rate estimated based on the required opening/closing motion.

CONSTITUTION: An intake passage A of each cylinder is opened/closed by a first opening/closing valve B, and a communication passage C which communicates at least to an intake passage downstream of the first opening/closing valve B is opened/ closed by a second opening/closing valve D. In this case, the first opening/closing valve B is delayed by a crank angle period which is more than one intake stroke and less than one combustion stroke than a required opening/closing motion and opened/closed by an intake air control means E. Also, an intake air flow rate sucked into a combustion chamber based on the required opening/closing motion is estimated by an intake air flow rate estimating means F. Moreover, a fuel supply amount is set by a fuel supply amount setting means G based on the estimated intake air flow rate. And based on the set fuel supply amount, a fuel supply means H is driven and controlled by a fuel control means I.