A method for manufacturing a ball joint in which a ball (8) acting as the centre of swivelling of a link mechanism and a holder embracing the ball are swivellingly or rotatably connected to each other, the method comprising a first step of casting molten aluminum alloy into a casting mold in which a ball (8) is inserted as a core so as to cast therefrom a holder (2) covering the ball (8) with a portion to which a shank (1b) is joined uncovered, a second step of heating the holder (2) to melt the aluminum alloy forming the holder (2), a third step of press contacting the shank (1b) against the ball (8) exposed from the holder (2), bringing electrodes (10a, 10b) into abutment with the shank (1b) and the holder (2), respectively, and causing a welding current to flow between the electrodes so as to projection weld the ball (8) and the shank (1b), thereby forming a shank with a ball, and a fourth step of applying an external force to the holder (2) or the shank with a ball so as to form a gap between the ball (8) and the holder (2).