An apparatus is provided for reproducing optical disks. An optical head irradiates linearly polarized light onto an optical disk. A change of a polarization orientation of light that is transmitted or reflected from the optical disk is detected in accordance with a recording signal on the optical disk. The apparatus moves the optical head into a pre-determined portion of the optical disk where write-once information is stored, and reproduces the write-once information after detecting a change of a polarization orientation of light that is transmitted or reflected from the pre-determined portion.