This invention allows super-resolution reproduction with which a better bER value is attainable, when information is recorded by a random pattern including a mark length not longer than a resolution limit, by use of a highly versatile signal decoding method.Information is recorded as marks and spaces coded by RLL(1,7) modulation, which each of the marks and spaces have one of a plurality of lengths, and 2T marks and 2T spaces of the marks and spaces being formed are shorter than 0.12 μm. An information recording layer (20) includes a reproduction film (21) and a reflective film (22) which are provided in this order from a side from which reproducing light is incident, which reproduction film is made of (i) zinc oxide, (ii) strontium titanate, (iii) titanium oxide, (iv) cerium oxide, or (v) a material including at least one of the (i) through (iv), and which reflective film is made of tantalum or titanium.