To substantially facilitate a manufacturing procedure at low cost by providing possibility of performing hardening in a continuously passing step.

A screw is formed of low alloy carbon steel, and comprises a head part, a holding part adjacent thereto, and a functional tip part of the hardness higher than that of the holding part in an external area of the limited depth in the radial direction. A screw body is formed by pressing and form rolling. In the screw manufacturing method for hardening the functional tip part, hardening is performed by instantaneous heating through the sophisticated energy transfer, and successive cooling, and limited to a circumferential part of the functional tip part.