To absorb frequency fluctuation occurring when a rotary speed of a disk is changed into a track jump phase and to prevent the frequency fluctuation from affecting recording/reproducing of a track address by constituting the track jump phase before a track address phase.

A TJ phase generation circuit 2 counts a period required for the TJ by using an inputted TACH signal to generate the TJ phase. Then, a TA phase generation circuit 3 counts the period required for the TA succeeding to the TJ to generate the TA phase. Then, a recording data phase generation circuit 4 counts the period required for the recording data succeeding to the TA, and after the circuit 4 generates a recording data phase, the residual period until a next TACH signal input 1 becomes a residual area phase. Further, a number of revolution control circuit 6 controls the rotation of the disk based on the TACH signal input 1, and thereafter, by constituting the TJ phase, the large frequency fluctuation occurring in the number of revolution control circuit 6 is absorbed into the TJ phase.