PURPOSE: To obtain an inexpensive, lustrous, and apparently beautiful gusset bag, by rendering a polyamide film of a laminate film made of polyamide film and polyolefin film as an external side, and by making the gusset bag wherein the whole edges including the external face of the folded part at one of the ends are fusion bonded.

CONSTITUTION: A gusset bag 1 is formed of a laminate film made of polyamide film 2 and polyolefin film 3 with the external face of the polyamide film 2. Next, the polyamide film 2 side of the laminate film 4 is moistened on the whole by a sponge roller or the like and subsequently the side edges thereof are superposed with each other by making the polyamide of the laminate film 4 outward with an automatic packer to seal vertically and then the bag is made flat in such a manner that the vertical seal part 6 be in the middle. The both edges being folded inward, it is sealed horizontally with keeping the state. The inner polyolefin face is not only fusion bonded but also the polyamide is fusion bonded at the same time. After the contents are contained in the bag, the bag is sealed horizontally and cut off. Usually, the horizontal sealing is carried out simultaneously with another horizontal sealing for the next bag and the middle of the both sealed parts is cut off.