An air vent device for a vehicle includes a main vent and an auxiliary vent divided by a partition wall and combined in a single air duct, a plurality of horizontal wings mounted at positions behind the main vent and the auxiliary vent, and an air volume control wing included in the plurality of horizontal wings for distributing an air volume discharged into an interior of the vehicle through the main vent and an air volume discharged into the interior of the vehicle through the auxiliary vent. The air vent device is capable of securing an interior discharge air volume, adjusting a wind direction, securing an air duct installation space, and re-distributing a leakage amount of air.