To provide a dust cover for a ball joint without any problem in which a seal lip part of the dust cover is separated from the axial part of a ball stud and a seal function deteriorates even in low temperature operation.

Concerning the dust cover for the rubber-like elastic material made ball joint tightened and fixed on a knuckle with the axial of the other end of the ball stud, held on the outer peripheral face of a cross section L-shaped retainer fitting and holding a small diameter opening part on the shaft part, and provided with a substantially drum-shaped film part projected to the outside connecting a large diameter opening part and the small diameter opening part, the seal lip part is formed on a face brought into contact with the outer peripheral face of the retainer of the small diameter opening part, a cut extended toward the side of the knuckle from the lower face of the small diameter opening part is provided, and a cylindrical holding part extended in the form of covering the outer periphery of the seal lip part toward the side of the knuckle from an outer diameter part of the retainer is provided in the cut.