In a bottle-shaped synthetic resin container having a body part of substantially rectangular tubular shape, groove ribs, having a comparatively wide vertical groove form, are depressingly provided at the centers in the width direction of flat wall portions of shoulder lower end parts, which are portions of a shoulder part that connect with the body part, to make these portions higher in rigidity and difficult to deform and, even when a deformation occurs, prevent the deformation from becoming a permanent deformation. Safe handling of the container is thus promoted, especially for the stacked storage of containers in a sideways-laid orientation.