To provide a rolled ball screw shaft which has a good precision groove and a low cost by restraining the stress by sudden plastic deformation generated when rolling of a ball screw shaft is started and minimizing the generation of an incomplete screw part.

A spiral ball groove 1a is formed on an outer periphery of this rolled ball screw shaft by rolling. The width T of the leading end chamfered part 6a of the ball screw shaft is set to 1/2-1 of the lead L of the ball groove 1a. Therefore, the good precision groove 1a can be formed by restraining the stress by sudden plastic deformation generated when rolling is started by setting the small diameter d1 of the leading end chamfered part 6a to groove bottom diameter d or less of the ball groove 1a.