There are provided a storage device for outputting-data in such a manner that whether or not error correction has been made can be discriminated, and a data processing system in which a storage device finishes data to a data processing device in such a manner that whether or not the area management information has been corrected for errors can be discriminated and in which the data processing device discriminates whether or not the area management information has been corrected for errors in order to perform predetermined data processing. There is also provided a data processing method for the storage device and for the data processing system. If there is any error correctable by an error processing unit 26 in the area management information read out from the flash memory 21, the controller 27 furnishes the area management information to the error correction processing unit 26 and appends a flag indicating the fact of error correction to the area management information corrected for errors to output the resulting data.