A plastic bottle is provided with a mouth, a main unit, for example, a flexible, cylindrical main unit, connecting the interior of the bottle with the mouth, a base structured to close the bottom portion of the main unit and have a greater rigidity compared to the main unit. The main unit includes a lower body section extending upward from the base, a central body section extending upward from the lower body section, and a crease between the lower and central body sections. The central body section can be configured to deform into a substantially flat shape through the action of external force F so as to bend outward.