Abstract: A ball joint includes a bearing seat crimped in place within a housing. A ball head of a ball stud slides in the bearing seat. A cylindrical crimpable portion of the bearing seat is inserted through a cylindrical portion of the housing. The bearing seat is fixed to the housing with two stopper portions. One of the stopper portions is formed by crimping the cylindrical crimpable portion against one of the ends of the housing. A dust cover is pushed between the ball stud and the other stopper portion. The stopper portion is enlarged outward using ultrasonic vibration. An inner side face of the cylindrical crimpable portion inclines outward at an angle ranging from 3.degree. to 20.degree. with respect to an axial direction of the cylindrical crimpable portion. A chamfered portion and rotation-stop portions, shaped like flower petals, are formed at one end of the housing.