To constitute a synchronization controller which is not affected by the distortion and unbalance of AC signals of software using a microprocessor, etc.

Three-phase AC signals are synchronized to the output of a frequency divider by means of a variable frequency circuit 13, by executing a program on a processor 21 at every divided frequency value set by means of the frequency divider 27, converting the three-phase AC signals into vectors on rotational coordinates in accordance with the program, then, binding the phase differences between the vectors and the reference axes of the rotational coordinates, and outputting the signals of the phase difference signals to the variable frequency circuit 13 from the processor 21 after amplification.