PURPOSE: To obtain the information recording medium having a large reproduction signal quantity by forming the recording layer of a thin film of an alloy consisting Al, Ca and X (X is an element selected from Se, Te and Ge).

CONSTITUTION: The information recording medium is constituted of a substrate 1 and by providing an inorg. protective layer 3, the optical recording layer 2, an inorg. protective layer 3, and an org. protective layer 4 successively on the substrate 1. Sputtering sources of Al and Ca and Te or Se are provided in a vacuum vessel 11 and the inside of the vessel is evacuated down to 5×10-6Torr in case of forming the recording layer. Gaseous Ar is then introduced into the vessel to control the pressure over the entire part in the vessel to 5×10-3Torr. The disk-shaped polycarbonate substrate is used and while this substrate is rotated at 60rpm, the sputtering rates of the respective elements are detected by a monitor and the electric power to be thrown to the respective sputtering sources is controlled to deposit the respective elements until the entire part attains 1,000 film thickness. The recording layer is thus formed. The information recording medium which is stable in the recording state, is increased in the reflectivity change arising from a phase transition and has the large reproduction signal quantity is thereby obtd.