Abstract: In a method for forming a lateral sealed portion, a liquid packing material can be filled without biting bubbles, granulates and so on included in the liquid packing material into the lateral sealed portion. In a method for forming a lateral sealed portion with a pair of lateral sealing rolls after a packaging film fed and run is folded at its central portion and a vertical sealing is performed at their side edge parts to shape into a cylindrical form and a liquid packing material is filled into an inside of the cylindrically formed packaging film, at least a folded side part of the cylindrically formed packaging film is pushed with a pushing means arranged between heat sealing bars located at equal intervals in a circumferential direction of the lateral sealing roll and the lateral sealed portion is formed at a pushed position with the pair of lateral sealing bars.