A data-recording/reproducing apparatus and method, that determine a reproduction position with high degree of reliability for data recorded on an information-recording medium even after the data is edited. From a process to edit an AV stream file, a DV data recording/reproducing apparatus splits a DVF-sequence into sequences including consecutive frames. When data is deleted in sector units in the edit process, pieces of data included in deleted frames are left at the beginning and end of each of the sequences. The DV data recording/reproducing apparatus records data representing the length of the data left at the head and the end of the sequences, data representing a frame number assigned to a frame located at the head of the sequences, and data representing the number of frames included in the sequences, on a disc used as the information-recording medium, for example an optical disc.