In order to bury watermark information in an original one-dimensional data, first a 1st spread one-dimensional data x(t) is generated by spreading the spectrum of the original one-dimensional data s(t) by using a PN series g(t). Then the 1st spread one-dimensional data is subjected to modified discrete cosine transformation. The specific frequency component value of the MDCT coefficient is so adjusted as to correspond to the watermark information. By subjecting the adjusted frequency component to the reverse conversion, a 2nd spread one-dimensional data x'(t) is generated. Lastly, by the reverse spectrum-spreading using the same PN series as those used in the spectrum-spreading, watermark one-dimensional data in which the watermark information is buried is generated.