Packing box, toner container, and method of assembling packing box

A method of assembling a packing box, comprising:

• folding a flat plate along multiple creases to form multiple edges to form a polygonal tube extending in a longitudinal direction to pack an object in the polygonal tube,
• the flat plate having:
• the multiple creases extending in the longitudinal direction;
• slits extending across the multiple creases in a direction orthogonal to the multiple creases;
• and
• ridgelines at both ends of the flat plate in the longitudinal direction to be polygonal rims of the polygonal tube, and
• the polygonal tube having:
• the multiple edges respectively corresponding to the multiple creases;
• and
• the polygonal rims:
• surround openings at both ends of the polygonal tube in the longitudinal direction, respectively;
• and
• have a shifted part in at least a part of the polygonal rims at both ends of the polygonal tube, the shifted part shifted from an imaginary plane orthogonal to the longitudinal direction;
• and
• making portions between the slits and the polygonal rims in the longitudinal direction project inward in a radial direction orthogonal to the longitudinal direction to form holding portions that hold the object, at positions corresponding to:
• two of the multiple edges at one end in the longitudinal direction;
• and
• two of the multiple edges at another end in the longitudinal direction.