A data nullification device for nullifying target data recorded on a recording medium is provided. The target data is made up of a plurality of data blocks. A judging unit (111) judges, in units of data blocks, whether the target data needs to be nullified. A nullifying unit nullifies, when a predetermined number of data blocks are judged as needing to be nullified or when one or more data blocks whose total amount of data reaches a predetermined amount are judged as needing to be nullified, the judged data blocks.
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