A operation of storing a post code, which is read from each servo frame on a target track of a disk recording medium, in a memory if an on-track condition for determining that a head is controlled to be positioned on the target track is satisfied is executed. Next, a operation of using the post code, which is stored in the memory, for a correction of a demodulation position if the post code corresponding to each servo frame is stored in the memory and the on-track condition is satisfied in the correction of the demodulation position in each servo frame is executed.