A ball joint, comprising: a ball; a resin sliding contact member having a sliding contact surface held in sliding contact with the ball, for covering a largest diameter portion of the ball, the resin sliding contact member comprising a first opening portion and a second opening portion that expose spherical surface parts of the ball in opposite directions; a holder formed through casting by using, as a core, the ball and the resin sliding contact member mounted so as to cover the ball, the holder comprising: a main body portion for covering a periphery of the resin sliding contact member; and a closing portion for covering the part of the spherical surface of the ball, which projects from the second opening portion of the resin sliding contact member, so as to be held in contact with the ball, the main body portion and the closing portion being molded integrally with each other, the holder being kept out of contact with the other part of the spherical surface of the ball, which is exposed from the first opening portion of the resin sliding contact member; and a shaft member joined to the another part of the spherical surface of the ball, which is exposed from the first opening portion of the resin sliding contact member, through electric resistance welding after the casting of the holder, to thereby construct a ball stud. a ball; a resin sliding contact member having a sliding contact surface held in sliding contact with the ball, for covering a largest diameter portion of the ball, the resin sliding contact member comprising a first opening portion and a second opening portion that expose spherical surface parts of the ball in opposite directions; a holder formed through casting by using, as a core, the ball and the resin sliding contact member mounted so as to cover the ball, the holder comprising: a main body portion for covering a periphery of the resin sliding contact member; and a closing portion for covering the part of the spherical surface of the ball, which projects from the second opening portion of the resin sliding contact member, so as to be held in contact with the ball, the main body portion and the closing portion being molded integrally with each other, the holder being kept out of contact with the other part of the spherical surface of the ball, which is exposed from the first opening portion of the resin sliding contact member; and a main body portion for covering a periphery of the resin sliding contact member; and a closing portion for covering the part of the spherical surface of the ball, which projects from the second opening portion of the resin sliding contact member, so as to be held in contact with the ball, the main body portion and the closing portion being molded integrally with each other, the holder being kept out of contact with the other part of the spherical surface of the ball, which is exposed from the first opening portion of the resin sliding contact member; and a shaft member joined to the another part of the spherical surface of the ball, which is exposed from the first opening portion of the resin sliding contact member, through electric resistance welding after the casting of the holder, to thereby construct a ball stud.