An air bag system includes an air bag folded so that an occupant-restraining face of the air bag which restrains an occupant upon a deployment is hidden inside a central portion of the folded air bag, and a retaining member for covering said folded air bag. The air bag is deployed by breaking a breaking portion provided on the retaining member, whereupon the retaining member is opened so that it is divided into a plurality of deployment-inhibiting portions, and the plurality of deployment-inhibiting portions are brought into engagement with an upper block and a lower block of an outer peripheral portion of the air bag deployed from the folded state, respectively, thereby delaying the deployment of the outer peripheral portion. Therefore, the occupant-restraining face of the folded air bag can be deployed at the very first to effectively restrain the occupant.