the present invention provides a disk for recording specified data having a plurality of helically formed track areas with one round of the circumferential direction of the disk as one track and a plurality of sector areas in which the plurality of track areas given track numbers added continuously from the outer peripheral direction of the disk are dividedly formed . the plurality of sector areas further include a plurality of data areas for storing the specified data and one parity sector for storing the parity of the specified data stored therein . the plurality of sector areas are given sector numbers added continuously from the starting positions of the track areas . in an information recording block having the plurality of sector areas included in the specified number of ones of the plurality of track areas , a plurality of parities recorded in the parity sector areas of these track areas are calculated by using different track and sector numbers .