A controller stores therein a sector address set indicating logical storage positions within a nonvolatile-memory storage area; page addresses indicating, in units of pages, physical storage positions within the nonvolatile-memory storage area; and pieces of management information each indicating whether one or more special sectors each being either a bad sector or a trimmed sector trimmed by a TRIM command are present in the corresponding page, while associating them with each other. When an access to a specified sector address is requested, the device refers to the piece of management information and judges whether any special sector is present in the page identified by the page address corresponding to the sector address. The device generates predetermined response data if the page contains one or more special sectors and accesses the nonvolatile-memory storage position corresponding to the sector address if the page contains no special sector.