A decoding device includes an interface unit, a readout unit that reads out a file and recording medium management information from an external recording medium, a decoding unit that analyzes a read out file, a storage unit that stores file analysis information and recording medium management information, a determination unit that determines whether or not the recording medium management information pieces are the same when the external recording medium is connected to the interface unit, and a matching confirmation unit that, when the recording medium management information pieces are determined as being the same, determines whether or not the file contents match. When the determination results in a mismatch, the decoding unit generates new file analysis information and performs file decoding using the generated file analysis information, and when the determination results in a match, the decoding unit performs file decoding using the file analysis information in the storage unit.