To provide a ball joint which exhibits a satisfactory sealing property by maintaining a proper assembling state of a dust cover with respect to a ball stud even when a film part of the dust cover is strongly pulled and which has an improved sealing property of the dust cover while maintaining a swingable range of the ball stud.

The ball joint includes: the ball stud 12 having a ball head part; a socket which stores the ball head part in a turnable manner and has an opening part on one side; and the dust cover 36, wherein the ball stud 12 includes a first shaft part 20, a flange part 22 having an outer diameter larger than that of the first shaft part 20 and a second shaft part 24 having an outer diameter smaller than that of the flange part 22, and wherein the dust cover 36 includes an inner circumferential part 44 fit to the first shaft part 20 and a lip part 48 to make close contact with the second shaft part 24.