A ball joint comprising: a ball stud having a spherical portion at one end on a lower side in a vertical direction of a shaft portion of the ball stud; a socket having a bearing for the spherical portion, the socket supporting the ball stud allowing it to freely rotate and swing; a coupling member coupled to the shaft portion on the other end side of the shaft portion; and a dust cover integrally including a deformable body portion, a fixed portion provided on one end side of the body portion and fixed to the socket, and a seal portion provided on the other end side of the body portion so as to slide on the shaft portion, the dust cover being made of an elastic body, wherein the coupling member includes a shaft hole into which the shaft portion is inserted and a gap that extends from the shaft hole to an outer wall surface of the coupling member, the shaft portion and the coupling member are coupled by a fixing device that pinches and fixes two surface areas sandwiching a part provided with the gap in the outer wall surface of the coupling member in a state in which the shaft portion is inserted into the shaft hole, the shaft portion of the ball stud includes an annular concave portion and an annular convex portion that is disposed at a position above the annular concave portion and below a coupling part between the shaft portion and the coupling member, an inner peripheral surface side of the seal portion of the dust cover is configured to be slidably in close contact with both of an outer peripheral surface of the annular concave portion and an outer peripheral surface of the annular convex portion, and an outer peripheral surface side of the seal portion is provided with a clamping member that clamps the seal portion to the shaft portion, and a top surface of the seal portion facing the coupling member is constituted by an inclined surface generated by the seal portion tapering down in diameter toward the coupling member. a ball stud having a spherical portion at one end on a lower side in a vertical direction of a shaft portion of the ball stud; a socket having a bearing for the spherical portion, the socket supporting the ball stud allowing it to freely rotate and swing; a coupling member coupled to the shaft portion on the other end side of the shaft portion; and a dust cover integrally including a deformable body portion, a fixed portion provided on one end side of the body portion and fixed to the socket, and a seal portion provided on the other end side of the body portion so as to slide on the shaft portion, the dust cover being made of an elastic body, wherein the coupling member includes a shaft hole into which the shaft portion is inserted and a gap that extends from the shaft hole to an outer wall surface of the coupling member, the shaft portion and the coupling member are coupled by a fixing device that pinches and fixes two surface areas sandwiching a part provided with the gap in the outer wall surface of the coupling member in a state in which the shaft portion is inserted into the shaft hole, the shaft portion of the ball stud includes an annular concave portion and an annular convex portion that is disposed at a position above the annular concave portion and below a coupling part between the shaft portion and the coupling member, an inner peripheral surface side of the seal portion of the dust cover is configured to be slidably in close contact with both of an outer peripheral surface of the annular concave portion and an outer peripheral surface of the annular convex portion, and an outer peripheral surface side of the seal portion is provided with a clamping member that clamps the seal portion to the shaft portion, and a top surface of the seal portion facing the coupling member is constituted by an inclined surface generated by the seal portion tapering down in diameter toward the coupling member.