A synthetic resin round bottle having a shape of the peripheral groove ribs that can increase the plane rigidity of the peripheral sidewall, without lowering the buckling strength in the vertical directions and the moldability of the bottle, including a round bottle having a neck, a tapered cylindrical shoulder, a cylindrical body, a bottom, a pair of peripheral groove ribs disposed at certain height positions of the body and formed in groove shapes, with one groove over the other groove in proximity to each other, where bases of these peripheral groove ribs are inclined relative to the direction of central axis of the bottle in a vertical sectional view, and the incline of a rib base for the upper peripheral groove rib has a direction opposite that of the incline of the rib base for the lower peripheral groove rib.