A packaging and filling device, a paper container, and a blank is disclosed. The blank comprises a sixth panel in a readily foldable state prior to a step for forming a bottom part, and provides sufficient length in a folded portion to protect the end surface of a packaging material. The blank for the paper container is formed by the packaging and filling device and comprises a top part, a bottom part, and a cylindrical body having four side walls and a square cross-section. The packaging and filling device comprises a loading unit for retrieving the blank and loading a cylindrical blank, a bottom-part-molding unit for molding the bottom part of the cylindrical blank to obtain a container, a filling unit for filling the container with liquid food from an upper opening, and an upper-part-sealing unit for heat-sealing the upper opening.