A vertical bag-making/filling/packaging machine (1) comprises: a film supplying portion (5) which lets out a film (F) from a roll (Fr); a bag-making guide (31) which folds the film (F) into a tubular shape and changes a conveying direction downward; a vertical sealing portion (60) which thermally seals side edges of the film (F) to each other in an up-down direction so as to make the film into a tubular shape; a film conveying portion (50) which conveys the film (F) downward; a filling portion (70) which loads a content (X) into an interior of the film (F); a lateral sealing portion (80) which thermally seals the film (F) in a left-right direction so as to make a bag body; a square-bottom sealing portion (90) which expands a bottom of the bag body to a rectangular shape from an inside and then thermally seals the bottom to form a rectangular bottom surface; and a cutter (89) which cuts off the bag body from the film (F).