The ball joint for the suspension system of automobiles, in which as a load-supporting seat, a multi-layer material provided with the synthetic resin layer having self-lubricating ability and abrasion resistance is used on the surface of the back metal, while as an opposite seat to a ball stud, synthetic resin having self-lubricating ability and wear resistance is used, and constituted so as to keep securely load support applied on the ball head by both seats.