A pouch in which an air layer can be formed with a simple mechanism using a single-tube air nozzle is provided. A pouch includes, in a side edge portion where a first and a second side-surface films are sealed, a non-sealed region which is not sealed over a predetermined length, and an opening provided near an upper end of the non-sealed region penetrating through the first and/or the second side-surface films. The non-sealed region includes an air filling portion which takes therein, through the opening, air from an air blowout hole of an air nozzle having a tip surface in a predetermined distance from the opening. The air filling portion is not sealed within a predetermined radius larger than a radius of the air nozzle such that, when the air filling portion expands due to increase of internal pressure, a part near the opening is adhered to the tip surface.