An improved storage bag comprises a bag body that defines an opening at a top thereof and two folding lines respectively at two opposing sides thereof. The bag body is provided with two handles respectively at the two opposing sides above the folding lines, so that when the bag body is extended into shape, the handles can be folded relative to the bag body along the folding lines to be overlapped horizontally. The bag body is provided with at least one support bar at each of the two opposing sides. Each support bar extends from a bottom of the bag body to an underside of one of the handles. The support bars can engage with the underside of one of the handles to support the bag body in the extended shape, thereby preventing the bag body from a collapse when the storage bag is in use.