The present invention relates to a method of manufacturing at least one flexible plastic container (10). According to the present invention, each container includes two separated walls (12, 13) facing each other, wherein the two separated walls are coupled to each other through a welding periphery end (14) of the container on a periphery of the container and define a storage space of the container (10). According to the present invention, the method comprises at least the steps of: a) forming a stack of two sheets (26, 27) made of a plastic material, wherein the sheets (26, 27) adhere to each other, and surfaces of the sheets (26, 27) facing each other make direct contact with each other without any elements forming an interfaces； b) forming the at least one container (10) without being previously separated by simultaneously molding the sheets (26, 27) attached to each other, wherein at least each container (10) is partially formed, and the sheets (26, 27) are maintained in a state that the sheets (26, 27) adhere to each other on at least a portion of areas of the sheets (26, 27) constituting the periphery end (14) of each container (10) when the container is molded； and c) welding at least partially the areas of the sheets (26, 27) constituting the periphery end (14) of at least each container (10).
