A folded-up air bag is accommodated in a module cover of a steering wheel, and a peripheral edge of an opening in the air bag is fixed to a retainer supporting an inflator. The folded-up air bag is covered from a rear side of a vehicle to a front side of the vehicle by a deployment-limiting sheet disposed along an inner surface of the module cover and fixed at one end thereof to the retainer. The deployment-limiting sheet is longer than a length of an inner periphery of the module cover in a longitudinal direction of the vehicle body. Thus, it is possible to inhibit the air bag from being expanded rearwards of the vehicle body at an initial stage of deployment by the deployment-limiting sheet, thereby avoiding the early interference with an occupant.
