Liquid blow molding apparatus and liquid blow molding method

A liquid blow molding method for liquid blow molding a preform into a container in a blow mold and supplying a liquid that has been pressurized to a predetermined pressure into the preform, the preform having been formed in a bottomed tubular shape, the liquid blow molding method comprising:

• using a liquid blow molding apparatus comprising a support pin disposed in the blow mold to
• support a bottom of the preform by the support pin by contacting a head of the support pin and the bottom of the preform at a time of a molding process when the preform is stretched in an axial direction of the preform and displace the support pin downward in accordance with deformation of the preform caused by liquid blow molding, wherein
• the support pin includes the head configured to support the bottom of the preform from an outer side of the preform and a shaft that is connected to the head and that is displaceable upward and downward in the axial direction of the preform,
• the support pin is configured to define a gap between the head and the bottom of the preform, the head and the preform spaced from each other when the preform is in a most ascended position where the preform is placed in the blow mold and the support pin is displaced most upward prior to stretching the preform and the support pin is configured to support the bottom of the preform when the preform is stretched by an amount of the gap in the axial direction, and
• the gap and a below-neck length that is an axial length from a lower surface of a neck ring to an end of the bottom of the preform satisfy the following formula (A):
• 0<gap≤0.44×below-neck length . . . (A).