In a reversible memory system, a pulsed laser beam generated from a laser unit is directed to a recording layer formed on a substrate 1. The recording layer essentially consists of a recording medium, for example, an iron-nickel alloy containing iron as a major component and 27 to 30 atomic % of nickel, which undergoes martensite transformation from a low-temperature phase to a high-temperature phase at a predetermined temperature Af and which undergoes a stress-induced transformation at a characteristic temperature Md. When a region of the recording layer is irradiated with the laser beam having a predetermined intensity, the region undergoes a stress-induced transformation so that the region is changed from the high temperature phase to the low temperature phase.