To provide a technology capable of easily and securely erasing unneeded data on a real data area without spending a large amount of time for data erasure even if a host system does not perform data erasure processing, as regards a disk device with a data erasure function.

In a disk drive 10, an erasure information management table 111 stored in a control memory 15 manages a state about the erasure of data on a real data area of a disk medium 110. Setting for controlling erasure of the data on the real data area is recorded in control information 112. An MPU 14 for drive control erases data being an erasure object in the erasure information management table 111 from the real data area of the disk medium 110 by overwrite erasure according to the setting of the control information 112.

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