A pressure bag (1) has a bag-like shape including an opening (11) at one end thereof and a bottom portion (12) on the opposite side to the opening (11). The pressure bag (1) has a double structure in which an inner sheet (20) and an outer sheet (30) are laid one on top of the other so that the outer sheet (30) is located on the opposite side of the inner sheet (20) from the housing chamber (10). A pressure chamber (15) is provided between the inner sheet (20) and the outer sheet (30). All of the inner sheet (20), the outer sheet (30), and the pressure chamber (15) extend from one side to the other side of the housing chamber (10) via the bottom portion (12).