A wide-neck synthetic resin container has a neck, a body and a bottom. A top side of the neck is sealed by a cap. The neck includes a neck tubular section, an engagement section protruding outward therefrom and engaging the cap, and a flange protruding outward at the top side. The flange protrudes less than the engagement section. The neck's top side includes a first top side formed by the neck tubular section, and a second top side formed by the flange that is the same height level with the first top side and increases an area of the top side. The neck tubular section has a uniform thickness at an area immediately below the flange and an area where the engagement section is formed. A thickness of the flange is smaller than that of the neck tubular section, and the neck has been crystallized.