Alternatively, the first and the second transmission substrates 1f and 1s are formed from plastic such as PC and the like or glass as smooth substrates, and the information pits 2f and 2s can be formed on the respective main surfaces thereof by means of painting of, for example, ultra-violet curing resin, pressing of the stampers and curing treatment, that is, a 2P method (Photopolymerization).