A digital video disk reproducing device utilizes a single memory both for error correction and for data buffering. The device designates a unit number to each sector of the memory and determines first, second and third regions. The first region corresponds to an absolute value of a unit number obtained by subtracting a unit number Y of a sector where a data read/write operation is completed during the descrambling from a unit number X of a start sector in an error correction block where the error correction is completed. The second region corresponds to an absolute value of a unit number obtained by subtracting a unit number Z of a sector where the data is completely transferred to the audio/video decoders or the ROM decoder from the unit number Y. The third region corresponds to an absolute value of a unit number obtained by subtracting the unit number Z from a unit number W of a sector where a writing operation of demodulated data is completed. Thereafter, the devices controls a W-pointer and a Z-pointer not to overfill a Z-pointer and a Y-pointer respectively, and controls an X-pointer and the Y-pointer not to pass ahead of the W-pointer and the X-pointer, respectively.