PURPOSE: To obtain a ball joint having a low sliding resistance between the spherical head part of a ball stud and the inner peripheral surface of a bearing by forming a plurality of micro-recesses in the spherical head part over the entire surface thereof, and by forming the boundary parts between the recesses and the inner surface of the bearing so as to have smooth curved surfaces.

CONSTITUTION: A plurality of micro-recesses 20 are formed in the outer surface 13 of a spherical head part 4 all over the surface thereof, and the boundary parts 21 between the recesses 20 and outer surface 13 of the spherical head 4 have smooth curved surfaces. Although the individual micro-recesses 20 have irregular shapes, the substantial part of the recesses 20 is relatively shallow, that is, it has a depth 20a small than its diameter 20b. Accordingly, when the ball stud 2 is used in a ball joint 1, lubrication oil retained in the micro-recesses 20 easily goes into and out from the recesses 20, owing to the sliding motion between the spherical head part 4 of the ball stud 2 and a bearing 6. Accordingly, it is possible to always feed lubricant to the outer surface 13 of the spherical head part 4.