To provide an infeed form rolling die capable of easily form-rolling a screw shaft for preventing a ball from being dropped, and to provide a screw shaft of a ball screw mechanism formed by using the die.

When the screw shaft 1 form-rolled by an infeed form rolling die is built in a ball screw mechanism, a ball 3 rolling in a male screw groove 1a is not rolled on dummy male screw grooves 1a', 1a' side because the phase of the male screw groove 1a is different from the phase of the dummy male screw grooves 1a', 1a', preventing the ball 3 from being dropped.