To continuously control a spring production device and to remove the error due to control response delay or dispersion, etc., by alternately controlling a follower shaft with a specific integral value when a feeding amount coefficient showing the feeding amount of the follower shaft against the movement amount of a main shaft is not an integral number.

A real feeding amount coefficient g is defined as an integer because a copy controlling circuit is a digital circuit composed of a counter, etc. Then, when it is the integer, a control command value is the largest integer g being not beyond g against the command feeding amount coefficient g, or g+1, however, when the follower shaft is controlled with an individual value of the feeding amount c coefficient g, or g+1, the error is always generated continuously. Therefore, in the copy controlling device, the feeding amount coefficient g1, g1+1 are switched alternately, the feeding amount of the follower shaft is controlled approximately and the set of the final position of the follower shaft is made as 0, and at the same time, the error on the way generating caused on the approximation is also minimized by finely dividing the section of approximation.