[Problem] To easily determine the matching/mismatching between the content and index files recorded on a recording medium when turning on power.[Means for Resolution] On a recording medium 2, there are recorded content files and an index file. The index file is constituted by attribute information of the content files (title text data, thumbnail-image data or the like). In the case of changing (recording or deleting) the content file, the index file is updated after the change. A computer 4 sets up, in a nonvolatile memory 15, status information indicative of being in a predetermined process stage, in the predetermined process stage from a start of changing the content file to a termination of updating the index file. The computer 4, at turning on power, determines the matching/mismatching between the content and index files recorded on the recording medium 2 by utilizing the status information, thus repairing the index file as required.