To provide an airbag device, capable of preventing a fish mouth phenomenon and achieving size and weight reductions of a retainer.

The airbag device has: an airbag 2; an inflator 3; the retainer 4; and an airbag cover 5. The airbag cover 5 has: a plate like part 51 constituting a vehicle interior surface; an inner case 52 arranged in the back surface of the plate like part 51 and constituting an inflation and development path of the airbag 2; and a plurality of holding holes 53 formed in the inner case 52 and capable of holding the retainer 4. The retainer 4 has: a support body 41 formed to be a nearly flat plate shape; a belt like body 42 inserted into the holding hole 53, attached to the support body 41 and formed annularly; a projection 43 formed on the under surface of the support body 41 and capable of locking one end of the belt like body 42; and a restriction plate 44 into which the projection 43 is inserted and which constitutes a stopper for the belt like body 42.