To obtain a high OW erasing rate and high CNR by controlling the absorptance for light of a recording layer in a crystal state to be higher than the absorptance for light of the recording layer in an amorphous state.

A dielectric film comprising such as ZnS, AlN and Ta2O5 is formed as a first protective layer 2 on a substrate 1, on which a recording layer 3 comprising such as a GeSbTe thin film and InSbTe thin film is formed. Then a light-absorbing layer 4 comprising a mixture film of SiO2 and W is formed on the recording layer. The first protective layer 2 and the second protective layer 5 act to increase the absorption efficiency of light in a recording layer or to largely change the reflected light before and after recording. Therefore, thickness of these protective layers, recording layer, light-absorbing layer and reflection layer is controlled in such a manner that the absorptance (Ac) for light of the recording layer in a crystal state is larger or equal to the absorptance (Aa) for light in an amorphous state (Ac≥Aa).