To provide a method of manufacturing a ball joint in which thermal influence given to a seat member by a high-temperature molten material can be reduced.

When the ball joint is manufactured, a spherical body 52 with seat is obtained by first assembling a seat member 6 onto the outside circumference side of a spherical body 51 that becomes a ball part. Then, the spherical body 52 with the seat is set in a mold 56, which has a projection part 55 of a shape that forms a hole part of a connection part of roughly a recessed shape of a housing. After that, the housing is formed by supplying the molten material into the mold 56 in such a way that a part of the material hits the projection part 55 and then flows to the outside circumferential side of the spherical body 52 with the seat.