A required intake air flow rate is converted to a post-model required intake air flow rate (BMtsm) by a base-system normative model, and the inverse model of an intake system model is used to calculate a base-system required throttle opening degree (BTA) so as to achieve the post-model required intake air flow rate (BMtsm). On the other hand, the required in-take air flow rate (Mt) is converted to a post-model required intake air flow rate (HMtsm) by a high-response-system normative model, and the inverse model of the intake system model is used to calculate a high-response-system required throttle opening degree (HTA) so as to achieve the post-model required intake air flow rate (HMTsm). Then, a target throttle opening degree (TAt) is set so as to fall within the range from the base-system required throttle opening degree (BTA) to the high-response-system required throttle opening degree (HTA) and the reduce a variation amount.