An optical disk apparatus for use with the combination type optical disk medium comprises an optical head capable of accessing the first and second recording layers and reading recording marks, a demodulator for applying a demodulation process to a signal read out of the first or second recording layer, an address converter for deciding from an optical disk reproduction instruction a recording layer to be accessed and performing conversion to a physical address of the recording layer, a reproduction controller following the recording layer determination and the physical address to control the optical head and the demodulator so as to control access and reproduction to and from the optical disk medium, and an instruction generator for generating an instruction to reproduce the optical disk.