Abstract: A proposal for reinforcing the bottom of a self-supportable parenteral bottle made of synthetic resin and having resting portions bulged downward from the bottom at opposite sides thereof, and a suspender flap downwardly projecting from and hingedly formed on a flat bottom portion between the resting portions on the center line of the bottom portion. The flat bottom portion has an endless ridge at its center, an upper flat bottom portion integral with and surrounded by the upper end of the ridge, and a lower flat bottom portion integral with and surrounding the lower end of the ridge, the lower flat bottom portion being gently sloped obliquely upward toward the center of the bottom, whereby the bottom of the bottle is precluded from bulging despite the thermal shrinkage resulting from molding or the rise of internal pressure due to sterilization by heating. The bottle is made self-supportable in an upright position reliably with good stability.