Embodiments in accordance with the present invention increase the reliability of a data storage device, and to reduce the circuit size. According to one embodiment of the present invention, a hard disk drive (HDD) executes not only error correction processing of data to be written to a magnetic disk, but also error correction processing of data stored in the DRAM. In the HDD according to this embodiment, one SRAM is shared by both kinds of error correction processing. As a result of executing the error correction processing of the data stored in the DRAM, the reliability of the HDD is improved. In addition, by using the same SRAM for the two kinds of error correction processing that differ from each other, it is possible to suppress the increase in circuit size.