PURPOSE: To ensure the high stability to the change of the ambient temperature and humidity of a disk recording medium, by forming an impermeable wet recording medium layer or a reflecting film on one side of a transparent resin substrate and a transparent impermeable wet film on the other side of said substrate respectively.

CONSTITUTION: A concentric or spiral signal track groove 2 is formed on one side of a substrate 1 made of a transparent resin material like polyvinyl chloride, polymethyl acrylate, etc. along with an impermeable wet recording medium layer 3 which changes its reflection factor or the like transmittance with irradiation of a recording light beam and a protecting layer 4, while a transparent impermeable wet film 5 of CaF2, SiO, etc. and a transparent protecting layer 6 are provided on the other side of the substrate 1. As a result, the balanced hygroscopicity is secured on both surfaces of the disk recording medium. At the same time, the warp is avoided for the recording medium.