PURPOSE: To facilitate a change into an integrated circuit by small circuit constitution by obtaining frequency difference and phase difference by one counter while computing controlled variables to each of frequency difference and phase difference and the adding section of both controlled variables by a software means.

CONSTITUTION: A fixed number counted by a counter 12 is set to a reference frequency alue, count values 13 are read by a CPU 16 every time the count values 13 counted by the counter 12 are latched to a counter latch 14, and the rotational frequency value of a motor 1 is acquired from the difference of two novel and old count values. Frequency difference is obtained by the difference of the reference frequency value and the rotational frequency value while a lower figure corresponding to the reference frequency value in the count values and the reference frequency value are compared and phase difference is acquired. Output values corresponding to each difference are obtained, and both output values are synthesized and output to a driver 20. Accordingly, the frequency control and phase control of a motor can be conducted without using complicate circuit constitution.