PURPOSE: To stably maintain recorded information by forming a recording layer of a specifically composed alloy.

CONSTITUTION: A substrate 1 is formed of a material which is transparent and is less deteriorated with age, for example, acrylic resin such as polymethyl methacrylate or glass. The recording layer 2 is formed on this substrate 1. The recording layer 2 is formed of the alloy having the compsn. expressed by the general formula (Sb100-xTex)100-yMy, where x, y are respectively in 20≤x≤80, 0<y≤20 range by atom.%, and M is at least one kind of the element selected from Au and Pt. The alloy having such compsn. range is changeable in phase between the crystalline state and the amorphous state and is stable in the amorphous state. The recording part of the information is thereby stably maintained and the deterioration of signals is decreased.