An optical disk apparatus for driving an optical disk on which a groove wobble corresponding to a signal acquired from frequency modulation of biphase modulated address information, and a mark for representing phase information placed inside the wobble are preformatted, and having the biphase bit count “a” (“a” is a natural number) between two of the adjacent marks, and the channel bit count “n” (“n” is a natural number) between two of the adjacent marks. The apparatus includes first clock signal production device for generating a first clock signal utilizing an “n” frequency multiple of the reproduction signal of the clock mark, wobble signal reproduction device for reproducing from the optical disk a wobble signal corresponding to the groove wobble, and frequency demodulation device for acquiring the address information by frequency demodulation of the wobble signal. The frequency demodulation device has a second clock signal generator for generating a second clock signal by frequency dividing a data clock signal supplied from the first clock signal reproduction device by 1/M(M - - - n/(a·s)) in which a clock “s” (“s” is a natural number) is an oversampling value of the biphase bit, a waveform shaping unit for acquiring binary values by waveforming the wobble signal, and a detector for acquiring the address information by processing the second clock signal using the binary signal.
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