Patent ID: 8657137

Claim:
A biaxially stretched, blow molded synthetic resin bottle with a bottom comprising a sunken bottom portion, which is formed by contouring and concaving a bottom plate upward in a direction of bottle inside, starting from an inner peripheral edge of a ground contact portion disposed along peripheral foot, the sunken bottom portion being capable of drawing upward in a reversible manner when internal pressure goes down, wherein this sunken bottom portion comprises: an inner peripheral wall portion standing from near the inner peripheral edge of the ground contact portion disposed along the peripheral foot, a central concave portion disposed at a center of the bottom, a reversible wall portion in a ring shape, which is reversibly deformable into an upward drawing state and which connects an upper end of the inner peripheral wall portion to base of the central concave portion, a circular rib wall portion is disposed between the reversible wall portion and an upper end of the inner peripheral wall portion so as to perform a function as a peripheral rib, and three radial ribs disposed on the outside of the central concave portion and formed in the radial direction from the central concave portion toward the peripheral foot, wherein the central concave portion has a shape in which its cross-section changes from a circular shape in an upper portion of the central concave portion to a regular triangular shape at a lower base portion, that is formed by connectin apexes of the three radial ribs.