An optical disk has a first substrate having a recording layer thereon, information to be recorded on the recording layer being reproducible with irradiation of a laser beam, a reflective layer formed on the recording layer, and a second transparent substrate, the laser beam being incident to the second substrate in reproduction. The first and the second substrates are bonded to each other by a bonding layer via the reflective layer. The bonding layer includes ultraviolet-hardened resin and at least one type of photochromic dye that is stable against the laser beam. In another type, the first substrate maybe transparent. Instead of the second substrate, this type has a hardcoat layer formed on a surface of the first substrate opposite to another surface thereof having the recording layer thereon, the laser beam being incident to the hardcoat layer in reproduction. The hardcoat layer includes ultraviolet-hardened resin and at least one type of photochromic dye that is stable against the laser beam.