An apparatus for recording and reproducing digital data according to the present invention, includes: a group converter; a controller; a recording converter; a recording unit; a reproducing unit; a reproducing converter; and a group reverse converter, wherein the group converter includes: a block management data generator for receiving the management data from the controller and generating block management data with respect to the corresponding blocked data, the block management data having a variable-length and containing information concerning each blocked data; a group management data generator for receiving the management data and generating group management data containing information concerning the entire grouped data; and a grouped data generator for receiving the blocked data, the block management data, and the group management data, and generating grouped data by arranging the blocked data, the block management data, and the group management data in a predetermined order.