A ball joint has a ball stud, a housing and a ball seat. The seat is an elastic body in a tubular shape with the top and the bottom being open, and has a spherical space to accommodate a ball portion. The housing has a spherical inner face that is close to an outer periphery of the ball portion, to accommodate the ball portion in the inner face via the seat so as to support the ball stud. A clamped portion arranged at a peripheral end of the housing is clamped to press the seat so that the ball stud can be swung and rotated.