A wrapping sheet is to be torn by the inflation of an air bag. Since attachment shafts, used to hold the folded air bag in position, are projected from the air bag, an engagement portion of the wrapping sheet is fitted on the attachment shafts, and the shape of a folding completed body of the air bag is maintained. The wrapping sheet includes not only the engagement portion, but also a coupled portion to be connected to the air bag, and a folding form control portion, which has an auxiliary engagement portion to be fitted on the attachment shafts. When the auxiliary engagement portion is fitted on the attachment shafts, the shape of the air bag that is being folded is adjusted.