PURPOSE: To join a housing onto an arm easily and firmly by pressing and caulking the projecting stage part on the outer peripheral surface of a housing in the axial direction onto the opened edge surface of the cylindrical part of the arm.

CONSTITUTION: A flange part 6 and a projecting stage part 18 are installed onto the outer peripheral surface of a housing 5 of a ball joint 1. A plurality of recessed parts and projecting parts are formed onto an opened edge surface 11 at one edge of the cylindrical part of an arm 10 onto which the housing 5 is press-fitted, and the opened edge 14 at the other edge of the arm 10 is set onto the flange 6 of the housing 5. The projecting stage part 18 of the housing 5 is caulked in the axial direction onto the opened edge surface 12 at one edge of the arm 10. Through this caulking, the edge surface of the caulked part 19 is bitten onto the projecting part of the edge surface of the arm, and the projecting edge surface is deformed, and the caulked part 19 is firmly fixed onto the opened edge surface of the cylindrical part of the arm 10.