When it is determined that an engine speed NE rapidly decreases (positive outcome at S210), a throttle increase amount TAu and a valve lift increase amount VLu are computed based on a decrease rate NEd of the engine speed NE (S220). Then, a target throttle opening degree TAt of a throttle valve and a target maximum valve lift VLt of an intake valve are increased by using the throttle increase amount TAu and the valve lift increase amount VLu (S230). As a result, a drop in the engine speed during idling is reliably suppressed.