Vehicle with a vehicle seat and a side airbag apparatus (100A,100B) installed in the vehicle, comprising: a bag shaped cushion which is housed in a seat back of a vehicle seat and expanded and deployed on the side of the vehicle seat utilizing gas supplied from an inflator; and a holding part (138A, 138B) for retaining the shape in the housed state of the cushion; wherein the cushion is wound or folded in a long shape in the vertical direction of the vehicle and housed in the seat back in the shape with the upper part or lower part thereof further folded back to the anterior of the vehicle, and wherein the holding part (138A, 138B) retains the upper part or lower part of the cushion which is folded back to the anterior of the vehicle, characterized in that the holding part (138A, 138B) includes: a cover member (140A, 140B) which is a flexible cloth material for covering the overall cushion in the housed state; and a window part (142A, 142B) which is opened by the cover member (140A, 140B), wherein the tip of the upper part or lower part of the cushion folded back to the anterior of the vehicle is passed from the inside to the outside of the cover member (140A, 140B), wherein, when the cloth material is sewn, the cover member (140A, 140B) is bag shaped and has a non-sewn part which is not sewn, with the cushion capable of being placed from the outside to the inside of the cover member (140A, 140B). a bag shaped cushion which is housed in a seat back of a vehicle seat and expanded and deployed on the side of the vehicle seat utilizing gas supplied from an inflator; and a holding part (138A, 138B) for retaining the shape in the housed state of the cushion; wherein the cushion is wound or folded in a long shape in the vertical direction of the vehicle and housed in the seat back in the shape with the upper part or lower part thereof further folded back to the anterior of the vehicle, and wherein the holding part (138A, 138B) retains the upper part or lower part of the cushion which is folded back to the anterior of the vehicle, characterized in that the holding part (138A, 138B) includes: a cover member (140A, 140B) which is a flexible cloth material for covering the overall cushion in the housed state; and a window part (142A, 142B) which is opened by the cover member (140A, 140B), wherein the tip of the upper part or lower part of the cushion folded back to the anterior of the vehicle is passed from the inside to the outside of the cover member (140A, 140B), wherein, when the cloth material is sewn, the cover member (140A, 140B) is bag shaped and has a non-sewn part which is not sewn, with the cushion capable of being placed from the outside to the inside of the cover member (140A, 140B). a cover member (140A, 140B) which is a flexible cloth material for covering the overall cushion in the housed state; and a window part (142A, 142B) which is opened by the cover member (140A, 140B), wherein the tip of the upper part or lower part of the cushion folded back to the anterior of the vehicle is passed from the inside to the outside of the cover member (140A, 140B), wherein, when the cloth material is sewn, the cover member (140A, 140B) is bag shaped and has a non-sewn part which is not sewn, with the cushion capable of being placed from the outside to the inside of the cover member (140A, 140B).