Method of fabricating a flexible container

In a method of fabricating a flexible container by sewing a plurality of sheets together, the method of fabricating a flexible container comprising:

• a first step of forming three or more approximately rectangular main sheets out of a longitudinal raw material sheet;
• a second step of setting an imaginary line passing through approximately the central part in the width direction of each of said main sheets to dispose a rectangular inlet sheet and outlet sheet on the imaginary line, sewing one end of each of said inlet sheet and said outlet sheet in the direction along said imaginary line to an end of the main sheet corresponding to the one end, and projecting the other end of each of said inlet sheet and said outlet sheet away from the main sheet in the direction along said imaginary line;
• a third step of respectively folding assembly sheets each constituted by said three types of sheets along the imaginary lines so that outwardly folding lines of the assembly sheets due to the folding conform to one another and the surfaces of the adjacent assembly sheets on the side of the outwardly folding lines are joined to each other;
• and
• a fourth step of sewing outer side edges of said adjacent assembly sheets together.