An air bag device mounted in an instrument panel has an inflator for supplying gas, a bag body having a gas inlet hole, and an inner bag disposed inside of the bag body. The inner bag is formed with a pair of first through-holes and a second through-hole so that an opening area of the first through-hole is larger than that of the second through-hole. The inner bag is expanded by the gas supplied from the inflator, while a large amount of the gas is discharged from the first through-hole. Accordingly, the air bag body is expanded toward the waist of a passenger on a passenger seat. At the same time, the gas is discharged from the second through-hole to flow along an inside of a windshield, whereby the air bag can be also expanded toward the head of the passenger. As a result, even if the inflator is mounted in the instrument panel at its upper portion, the air bag device can securely protect the passenger on the passenger seat.