An airbag apparatus according to the exemplary embodiment of the present invention includes: an airbag which is inflated when gas flows into the airbag, and has a left opening hole formed in a left surface, and a right opening hole formed in a right surface; and a cylinder which is disposed in the airbag while connecting the left opening hole and the right opening hole, and has a vent hole through which the gas flowing into the airbag is discharged.