To provide a process surely removing fine stains on a screw and manufacturing the screw with extremely smooth surface in assembling an electronic precision device.

A fowling removal process for manufacturing a threaded fastener, in which a threaded fastener is formed by means of rolling ridges in the leg at a rolling process 2, is subjected to a treatment at a surface hardening process 3, and is washed in a rinsing process 4, comprises; a surface polishing process 5 for polishing a surface of the threaded fastener following the rinsing process 4; and a cleaning process 10 for removing metal powders, dusts, oils, and the like, which result in a complete removal of metal powders, dusts, oils, and the like which generate in production; and thus provides such a clean threaded fastener without fine fouling that an electronic precision device therewith can work normally without receiving the bad influence and have a long life and a stable quality.