A first data-recorded region is formed in one of multiple recording layers of a rewritable optical disc before a second data-recorded region is formed therein. A first on-disc position is related to an innermost position within the second data-recorded region. Information is reproduced from a recording management area of the disc. A second on-disc position is derived from the reproduced information. The second on-disc position is in substantial coincidence with an outermost position within the first data-recorded region. The first on-disc position and the second on-disc position are compared to decide whether an unused portion is present in or absent from a region therebetween. When the unused portion is present, padding data is recorded thereon. The second on-disc position is updated into substantial coincidence with an outermost position within the second data-recorded region. The information in the recording management area is updated to reflect the updated second on-disc position.