there is provided a ball joint provided with a ball stud having a spherical head portion in an end portion , a ball seat to which the spherical head portion is slidably fitted , thereby pivoting the ball stud universally , and a housing receiving the ball seat , the housing being structured such that a closed - end cylindrical main body portion and a flange portion extending outward in a radial direction from an edge portion of the main body portion are formed in accordance with sheet metal processing . the flange portion is formed thinner than a thickness of the main body portion .