PURPOSE: To improve chemical stability and the contrast of signals by using a thin alloy film which consists essentially of Ni and In and contains In at 10W65atom.% as a recording layer.

CONSTITUTION: The thin alloy film 2 which consists essentially of Ni and In and contains In at 10W65atom.% is deposited and formed as the recording layer by a 2-sources vapor deposition method on a high-polymer substrate (polyimide) 1 and a protective SiO2 film 3 is formed by a vapor deposition method on this thin Ni-In alloy film 2. This recording layer is changed in optical characteristics when the layer is quickly heated or slowly cooled by laser light. The optical recording medium which has the excellent chemical resistance such as moisture resistance and the high contrast is thereby obtd.