Provided is a method for manufacturing a synthetic resin container, including: after the shaping of a container, drawing back a liquid inside the container to a pressurized liquid feeding unit side by a suckback mechanism disposed at a predetermined position in a feeding channel of the liquid from the pressurized liquid feeding unit to a mouth tube portion of a preform; closing the feeding channel by means of a valve mechanism disposed on the downstream side of the suckback mechanism; introducing a gas into the container so that the volume reduction deformation of the container resulting from the drawing back of the liquid is restored to its original shape; and adjusting a headspace inside the container with the amount of volume change associated with the volume reduction deformation.