A retaining cover that encapsulates a cushion which is stowed in a bulk stowed form in front of the regular seating position of the vehicle having a side surface retaining part wound around a side surface of the cushion in stowed form, a cloth-like part provided in a manner traversing vertically across the upper surface of the cushion in stowed form, and a weak part provided at a prescribed location on the cloth-like part that divides the cloth-like part to an upper piece and lower piece due to the expansion pressure of the cushion. If the cushion expands and deploys with the occupant in close proximity, the upper piece of the cloth-like part is sandwiched in between the cushion and the occupant, such that the upper piece restrains the upward deployment of the cushion.