To provide a nonvolatile storage device that uses a high-capacity flash memory having many physical blocks and can execute retrieval of an empty block in a short time.

The addresses of the physical blocks after data writing are listed on a logical/physical conversion table 106, and the addresses of the physical blocks after data deleting are listed on an empty block table 107. A controller 104, in writing data in the flash memory 103, (a) selects the address of an arbitrary physical block in which effective data is not written from the empty block table 107, and writes data into the physical block of the address, and (b) stores the address of the physical block in which data is written in the logical/physical conversion table 106 in a form corresponding to the logic address provided from the outside.

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