PURPOSE: To need no reference point match at the time of starting and shorten a synchronous desired time and simplify synchronous operation, by setting the Z-phase pulse signal of the original signal of an encoder, as a reference, and by controlling the speed of a follow-up side machine.

CONSTITUTION: By a phase difference detection circuit 8, each Z-phase pulse signal of encoders 3a, 3b is respectively set as clear and latch signal, and the pulse number of four-times frequency pulse signal from a frequency multiplication direction discriminating circuit 6a included in a difference period at the time point of the generation of both the signals is counted. Then, with the reference of the rotating state of the encoder 3a, a phase difference α between both encoder original-points is detected. The input of the phase difference αto an angle regulating circuit 12 is provided, and a correction angle γ is corrected.