| 摘要 |
By forming a resin sheet or a metal sheet, an angular-box-shaped bag main body having gore portions on surrounding side faces to ensure its height is formed. A valley line is formed in an intermediate portion of each of the gore portions in a height direction. A triangular overlaid and folded portion is formed in an end of each of the gore portions on each of the surrounding side faces with each corner portion of the angular-box-shaped bag main body being sandwiched between one surrounding side face and another surrounding side face adjacent to the one surrounding side face in which the gore portion is folded in an overlaid manner in the overlaid and folded portion at a same time when another gore portion on another surrounding side face is folded. The angular box-shaped bag main body is folded so as to be in a flat state by allowing each of the gore portions to be folded in a manner to form a valley line along the folded line.
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