An airbag device 1 includes a retainer 14, a bag body 12, and an inflator 13. The retainer 14 is installed on the inner side of a deployment wall 15 of an instrument panel 11 that is openable by breaking. The retainer 14 has a bottom wall 14B arranged opposite to the deployment wall 15, and a front side wall 14F continuous with the bottom wall 14B. The bag body 12 is folded in a deployable manner, and is held in the retainer 14 in the folded state. The inflator 13 is installed in the front side wall 14F of the retainer 14, and generates gas to be fed into the bag body 12 when impact is inputted. All folded parts of the bag body 12 are arranged on the side closer to the deployment wall 15 than an end part of the inflator 13 on the side of the bottom wall 14B of the retainer 14.