PCT No. PCT/JP97/00865 Sec. 371 Date Sep. 18, 1998 Sec. 102(e) Date Sep. 18, 1998 PCT Filed Mar. 18, 1997 PCT Pub. No. WO97/35309 PCT Pub. Date Sep. 25, 1997In a recording and reproducing apparatus for a disc-shaped recording medium, and a defect substitution method for a disc-shaped recording medium, whether reproduction of recorded data is good is determined by sector unit and not by product code unit, defective sector discrimination is performed by sector unit, and only sectors determined defective are alternately recorded, when using a recording format in which data that is error detection and correction coded with a product code is segmented and recorded to a plurality of sectors.