To provide a driver seat air bag device whose horn operating structure is simple in structure, costs low, and can surely actuate a horn.

In an air bag module 1 in which a bag cover 14 is fixed to a substantially rectangular retainer 2 provided with an air bag and a gas generator 8, the retainer 2 is provided with a bottom plate part 3, which is provided with a gas generator mounting hole in the center, and vertical wall parts 12 on respective side parts, and projection pieces 13, which are protruded outward respectively, are formed in the vertical wall part 12 or in the bottom plate part 3. In the bag cover 14, leg piece parts 22 surrounding the vertical wall parts 12 in the retainer 2 are formed on the back face side, and in the leg piece parts 22, locking holes, to which the projection pieces 13 are inserted so as to lock the retainer 2, are formed in the positions matching with the projection pieces 13 in the retainer 2. In each of the corner parts of the bottom plate part 3 in the retainer 2, a supporting piece 24, which is brought into contact with the lower end face of the leg piece part 22 in the bag cover 14 so as to support the lower end face, is formed.