Ball seat, ball joint, and method for producing ball joint

A method for producing a ball joint, the ball joint comprising:

• a ball stud including a stud portion having one end portion connected to a structural member and another end portion, to which a spherical ball portion is integrally joined;
• a housing made of metal and configured to support the spherical ball portion of the ball stud to allow swinging and rotating movement of the spherical ball portion, the housing having a space that opens to one side thereof;
• and
• a ball seat made of plastic and interposed between the housing and the spherical ball portion, the ball seat including a plurality of protrusions jutting out from the ball seat and inserted into a plurality of through holes formed in a bottom portion of the housing, wherein the protrusions having pierced through the through holes are staked at their distal portions, and a protrusion has a large diameter portion, whose diameter is larger than an inner diameter of a through hole of the housing, at its proximal portion proximal from a distal portion thereof, the method comprising:
• inserting the large diameter portion, while compressed, through the through hole of the housing, and
• protruding the distal portion of the large diameter portion having been inserted through the through hole outward from the through hole toward outside of the housing.