A synthetic resin container has improved formability while preventing deformation of corner walls. The synthetic resin container includes a mouth that serves as a dispensing opening for contents, a body that is continuous with the mouth via a shoulder, and a bottom that closes a lower end of the body. The body includes a pair of main walls arranged so as to face each other with a gap therebetween, a pair of side walls arranged so as to face each other with a gap therebetween, and corner walls that couple respective ends in a circumferential direction of the main walls and the side walls. Each corner wall is provided with U-shaped ribs that are formed in a substantially U-shape within a surface of the corner wall and that are concave toward an inner side in a thickness direction of the corner wall.