A data storage apparatus includes: a medium for storing data having synchronization marks and data blocks, the synchronization mark and the data block being allocated alternately in the circumference direction of the medium; a head writing data into or reading out data from the medium; and a processor for executing a process including: reading out synchronization marks, measuring time for the head to pass through each of the data blocks based on signals read out from each of the synchronization marks in the circumference direction, generating write/read clock for each of the data blocks, which is continuously changing in speed, by calculating difference in time for the head to pass through the each one of the data blocks and its adjacent one of the blocks on the basis of the time measured, and writing data into or reading out data from the medium in synchronization with the write/read clock.