Bottom structure of bottle-shaped container made of synthetic resin

A bottom structure of a biaxially-oriented blow-molded bottle-shaped container made of a synthetic resin, comprising a neck, a shoulder, a body and a bottom, wherein

• the bottom has a connecting cylindrical wall, a tapered-cylindrical wall, a bottom wall and a grounding wall,
• said connecting cylindrical wall connects to a lower end of the body,
• said tapered-cylindrical wall connects to a lower end of the connecting cylindrical wall,
• a diameter of said tapered-cylindrical wall is decreased downwardly at a certain inclined angle,
• said bottom wall is domed to an inside of the container,
• said grounding wall is formed in a ring plate shape, and is arranged between a lower edge of the tapered-cylindrical wall and a lower edge of the bottom wall,
• each of a plurality of groove ribs is formed from an upper edge of the tapered-cylindrical wall through the grounding wall to the lower edge of the bottom wall,
• the groove ribs are arranged with isometric center angle, and extend radially, and
• a plurality of reinforcing ribs are formed from proximate an upper, central portion of the bottom wall towards the lower edge of the bottom wall, the reinforcing ribs not connected to the groove ribs, wherein the tapered-cylindrical wall is formed in a regular polygonal truncated-cone shape having side edges of which number is the double of a number of the groove ribs, and the groove ribs form alternate side edges of the regular polygonal truncated-cone shape.