An optical disk from which address information is read stably and efficiently. The optical disk has a plurality of tracks each of which is divided into a plurality of recording sectors and each recording sector has a header area. In the header area, address information for recognizing the position of the corresponding recording section and address synchronization information for bit synchronization by recognizing the recording position of the address information are recorded. The address information is modulated with a run length limiting code of maximum inversion interval Tmax bits (Tmax is a natural number) and the address synchronization information includes two patterns of inversion interval (Tmax+3) bits. Therefore, the reproduced signal of the address synchronization information is distinguished from the reproduced signals of other information.