Provided is a technique whereby a DLC film having a desired surface roughness and a desired film hardness can be easily formed within a short period of time while preventing cost increase so that a large quantity of boll joints, which are less expensive and yet have stable sliding characteristics, can be supplied. A method for manufacturing a ball joint provided with a ball stud that has a spherical surface section and a holder section that pivotally holds the spherical surface section, said method comprising: an intermediate underlayer-forming step for forming an intermediate underlayer, that has a fine irregular surface structure, on the surface of the spherical surface section using a sputtering method; and an amorphous hard carbon film-forming step for forming an amorphous hard carbon film, that has a root mean square roughness on the surface of 6.5-35 nm, on the intermediate underlayer using a PIG plasma film formation method.