The present invention provides a packaging and filling device, a paper container, and a blank in which it is possible to put a sixth panel in a readily foldable state prior to a step for forming a bottom part, and obtain a sufficient length in the folded portion necessary for protecting the end surface of a packaging material. For a blank for a paper container which is formed by a packaging and filling device and which has a top part, a bottom part, and a cylindrical body having four side walls and a square cross-section, the packaging and filling device comprise a loading means for retrieving the blank and loading a cylindrical blank, a bottom-part-molding means for molding the bottom part of the cylindrical blank to obtain a container, a filling means for filling the container with liquid food from an upper opening, and an upper-part-sealing means for heat-sealing the upper opening.