In the ordinary operation mode, a data storage apparatus writes data into a first flash memory, while writing ECC data, which is used for correcting the data written in the first flash memory, into a second flash memory. When there is no remaining storage space in the first flash memory, the data storage apparatus deletes existing ECC data previously written in the second flash memory and writes ordinary data into the second flash memory. This arrangement enhances the reliability of data and enables effective use of the original storage space in the system of data storage with multiple storage areas.