A ball joint includes a bearing seat in the form of a resin ball seat provided within a seat-accommodating portion of a metal socket for slidably and rotatably receiving a ball portion of a ball stud. An end portion of the seat-accommodating portion through which the stud portion passes extends towards the stud portion beyond the spherical center of the ball portion. The ball seat has a covering portion formed on the outer side of a seat opening portion of a ball-accommodating portion which has a spherical shape conforming to a sliding surface of the ball portion of the ball stud. The covering portion is formed by bending the seat opening portion such that it covers the outer periphery of the opening portion of the seat-accommodating portion of the socket.