PURPOSE: To easily manufacture a scale shaft having comb-teeth shaped slit parts and flat parts by rolling a work material using, as a rolling die, a cylinder having a circumferential surface of integer times a circular arc of an uneven structure oposite to the uneven structure on a circular arc having one pitch of a scale shaft.

CONSTITUTION: The scale shaft 20 is proved with flat parts as chords AB, CD, EF, at an equal distance, at three places on the circumference. Therefore, when a part from a start point C to C, D, E including a circular arc DE also on the summit part of the comb-teeth is taken as one pitch, a circular arc developed by three pitches on a circular arc 21 of a circles larger in radius than the scale shaft 20 is C', B', A', F', E', D', C'. If the radii of the dies 21, 22 are set so that the circular arc of the die 21 takes integer times the length of the profile of this one pitch or C', D', E' these dies can be used as rolling dies.