A ball joint wherein a ball seat having a closed side is insertewd between an inner surface of a housing and an outer surface of a ball portion of a ball stud, the ball seat being formed of a hard synthetic resin, and having an annular flange after on the closed side of the ball seat engaged with an opened edge at one side of the housing, an annular flange engaged with an opened edge at the other side of the housing, and an annular recess provided on the inner circumferential side of the annular flange on the closed side of the ball seat and enabling the same annular flange.
