A flexible package, comprising: a first side-surface film, a second side-surface film, and a bottom film which are joined together, the bottom film being inserted between the first side-surface film and the second side-surface film so as to be folded in half and inserted from a fold line side, with a predetermined insertion length; and a storage part formed by sealing peripheral portions of the films excluding a portion through which contents are to be injected, the storage part having a lower bottom surface which is the bottom film, wherein on only one of two side edge portions which are sealed regions of the peripheral portions at both side ends of the first side-surface film and the second side-surface film, a non-sealed region is provided which is surrounded by the sealed regions and is not sealed over a predetermined length in a top-bottom direction, the non-sealed region has a uniform diameter of 3 to 50 mm and is configured to form a gas injection portion by a gas being filled therein, regarding the non-sealed region, a distance, along an extending direction of the non-sealed region, from an upper end of the non-sealed region to an upper end portion of the flexible package where an end portion of the first side-surface film and an end portion of the second side-surface film overlap each other, in a state where the first side-surface film and the second side-surface film are flat, is less than or equal to 30% of a height of the flexible package which is a distance from a lower end of the bottom film to the upper end portion along the extending direction of the non-sealed region, in the state where the first side-surface film, the second side-surface film, and the bottom film are flat, at an upper end of the other one of the two side edge portions of the flexible package, a discharge part is provided such that a lower end thereof is located beneath the upper end of the non-sealed region, along the extending direction of the non-sealed region, in the state where the first side-surface film and the second side-surface film are flat, the storage part is separated from the non-sealed region by the sealed regions having a predetermined width, the discharge part is a sealed spout sandwiched between the first side-surface film and the second side-surface film. a first side-surface film, a second side-surface film, and a bottom film which are joined together, the bottom film being inserted between the first side-surface film and the second side-surface film so as to be folded in half and inserted from a fold line side, with a predetermined insertion length; and a storage part formed by sealing peripheral portions of the films excluding a portion through which contents are to be injected, the storage part having a lower bottom surface which is the bottom film, wherein on only one of two side edge portions which are sealed regions of the peripheral portions at both side ends of the first side-surface film and the second side-surface film, a non-sealed region is provided which is surrounded by the sealed regions and is not sealed over a predetermined length in a top-bottom direction, the non-sealed region has a uniform diameter of 3 to 50 mm and is configured to form a gas injection portion by a gas being filled therein, regarding the non-sealed region, a distance, along an extending direction of the non-sealed region, from an upper end of the non-sealed region to an upper end portion of the flexible package where an end portion of the first side-surface film and an end portion of the second side-surface film overlap each other, in a state where the first side-surface film and the second side-surface film are flat, is less than or equal to 30% of a height of the flexible package which is a distance from a lower end of the bottom film to the upper end portion along the extending direction of the non-sealed region, in the state where the first side-surface film, the second side-surface film, and the bottom film are flat, at an upper end of the other one of the two side edge portions of the flexible package, a discharge part is provided such that a lower end thereof is located beneath the upper end of the non-sealed region, along the extending direction of the non-sealed region, in the state where the first side-surface film and the second side-surface film are flat, the storage part is separated from the non-sealed region by the sealed regions having a predetermined width, the discharge part is a sealed spout sandwiched between the first side-surface film and the second side-surface film.