BAG BODY

Provided is a bag body which has a flatter shape in its expanded state. This bag body has control yarn therein, which controls expansion. The control yarn includes: a first seam which extends from a non-expansion section to another non-expansion section within the bag body; a second seam which is a seam forming the fabric on one surface of the expansion section of the bag body, and is formed by being separated from the fabric on said one surface, threaded through the first seam, and turned back to the fabric on said one surface; and a third seam which is a seam forming the fabric on the other surface of the expansion section of the bag body, and is formed by being separated from the fabric on the other surface, threaded through the first seam, and turned back to the fabric on the other surface. A control seam group, which is configured from the first to third seams, includes: a first seam unit that is configured such that the two or more second seams alone are consecutively threaded through the first seam; and a second seam unit that is configured such that the two or more third seams alone are consecutively threaded through the first seam. The first and second seam units are alternately arranged in the direction in which the first seam extends.