The present invention relates to an airbag for a vehicle including: an inflator which discharges high-pressure gas; an airbag cushion which has a vent hole so as to discharge a part of the high-pressure gas; a vent hole cover which is installed to shield the vent hole; and an operating unit which allows the vent hole cover to shield the vent hole when a predetermined time has passed at the time of deploying the airbag cushion, and provides advantages in that the severity of a neck injury to an occupant is reduced, and regulation satisfaction by the United States New Car Assessment Program (US-NCAP) is improved.