Provided are a ball joint and a dust cover that make it possible to suppress contact of a body portion of the dust cover with the vicinity of a flange portion of a ball stud. A dust cover integrally includes: a deformable bellows-shaped body portion made of an elastic body; a fixed portion made of an elastic body and provided on one end side of the body portion; and a sealing portion made of an elastic body and provided on the other end side of the body portion. The sealing portion includes: an inner peripheral sealing portion configured to be slidable on a part of a shank portion on the opposite side of the shank portion from a spherical portion with respect to a flange portion; and a cover portion that continuously covers, in an outer wall surface of the flange portion, a radially outward tip end portion and a part of a portion that decreases in diameter from the tip end portion toward the spherical portion side.