Provided is an apparatus and method for manufacturing a ball joint that are capable of reducing a torque applied between a ball stud and a ball seat.The ball joint manufacturing apparatus includes an upper mold having a shape configured to injection-mold a ball seat formed of a synthetic resin material and surrounding the outside of a spherical head part of a ball stud; a lower mold installed under the upper mold and having a molding surface for forming a portion of the ball seat; a fixing jig configured to fix the ball stud to a molding position of the upper mold and the lower mold; and a rotary member configured to rotate the fixing jig.