An airbag system includes: a first left chamber that is expandable so as to cover an outer surface of a front left pillar which is located on a left side with respect to a vehicle width direction of a vehicle; a second left chamber that is expandable on the first left chamber; a first right chamber that is expandable so as to cover an outer surface of a front right pillar which is located on a right side with respect to the vehicle width direction of the vehicle; a second right chamber that is expandable on the first right chamber; a recognition portion that recognizes a risk object which is present in a vicinity of the vehicle; a prediction portion that predicts a collision between the risk object and the vehicle; and an expansion control portion that performs an expansion control of the first left chamber, the second left chamber, the first right chamber, and the second right chamber based on a prediction of the prediction portion.