PURPOSE: To obtain a medium with excellent heat resistance and chemical resistance, and little vapor permeation and vapor absorption by using a transparent substrate comprising specific fluorinated cycloaliphatic hydrocarbon polymer.

CONSTITUTION: The transparent substrate consists of fluorinated cycloaliphatic hydrocarbon polymer having a recurring unit expressed by formula I or formula II. In formulae, (n) is positive integer and is a cyclohexane ring. Thereby, the medium has excellent heat resistance and chemical resistance and little vapor permeation and little vapor absorption. Reliability of this optical recording medium is improved compared to the one using polycarbonate resin or acrylic resin as a transparent substrate.