Provided are a cylindrical container inner bag and a composite container using the cylindrical container inner bag for the purpose of easily filling the cylindrical container inner bag housed in a cylindrical container with a filler to the substantially same capacity as that of the cylindrical container. The cylindrical container inner bag formed in such a manner that one or more films folded back or overlapping with each other are closed at least at a right or left end portion or a lower portion has a filler housing portion and a support mechanism portion positioned below the filler housing portion. The support mechanism portion has a support mechanism configured to regulate the position of the bottom of the inner bag in a cylindrical container.