PURPOSE: To freely execute a format with a user and to prevent a seeking operation from decreasing by writing track address information on a track address area at the time of disk preparation, and preventing the format from being executed for the area other than the above area.

CONSTITUTION: At the time of an optical disk D preparation, track addresses are written on plural track address areas 1 of the optical disk D, and the format is not executed for the area other than the above area. Consequently, the user can freely execute a format by using a free format area 2, and since a seeking operation is executed based on the information written into the area 1, the seeking operation is not prevented from decreasing.