PURPOSE: To obtain an information recording and erasing method capable of performing recording and erasure at high speed by forming such a state that an amorphous phase and a non-equilibrium crystal phase are mixed to the laser beam irradiated part of a recording layer and allowing the irradiated part to correspond to a recording state or an erasure state.

CONSTITUTION: A substrate 1 is formed from a material such as plastic, for example, polyolefin or glass and a protective layer 3, a recording layer 2, a protective layer 4 and a protective layer 5 are formed thereon in this order. The recording layer 2 is formed from a material capable of generating such a state that an amorphous phase and a non-equilibrium crystal phase are mixed by the irradiation with laser beam. In this state wherein the amorphous phase and the non-equilibrium crystal phase are mixed, the non-equilibrium crystal becomes a nucleus and the amorphous phase is crystallized extremely rapidly. Therefore, recording and erasure speeds can be made high. As a material capable of generating this phase change, there is In-Sb-Te. For example, when the recording layer 2 is formed from In-Sb-Te, a state wherein the amorphous phase and the non-equilibrium crystal phase are mixed appears in a boundary region where the amorphous phase and the non-equilibrium crystal phase appear in such a case that the recording layer is melted and quenched by the irradiation with laser beam and initialization, recording and erasure can be accelerated.