To provide an irregular container to be easily taken out of a hard case storing a plurality of containers in the filled state, provided with self-supporting properties and reducing the manufacturing cost.

One of both end openings of a cylindrical film of given length is heat sealed liquid-tightly (a sealing section 2) to form a bag face 17. The other side of the opening including a mouth cap 13 is heat sealed (the sealing section 2 and a mouth cap bonding section 4) to form an upper face. A bag- shaped body thus formed is pressed from both sides in the state of facing the folding angle of the cylindrical film so that the section of the bag-shaped body is formed into the rectangular parallelepiped, and the roots of the triangle protruded sections formed on the upper face and the bottom face 17 of the rectangular parallelepiped shape are heat sealed on the sealing lines of the opening orthogonally and horizontally (a sealing section 5), and a triangle face outside the seal of the bottom face 17 is cut and removed, and a finger setting hole 15 is opened on a lug section 6.