A digital audio tape recorder (DAT) is used as a digital data storage recorder, and digital signals containing main data and sub-data are recorded in separate areas in each track of a plurality of tracks formed on a recording medium (15). A predetermined number of tracks constitute a group (GP) and a plurality of groups are recorded on the medium (15); in the sub-area an identification signal (R-ID) is further recorded which indicates whether or not main data recorded in the main areas of a given group is the same as the main data recorded in the main areas of preceding and subsequent adjacent groups. When identical data is multiply written for a plurality of units, a division of the multiply-written portions is detected, and signal processing is facilitated.
