When a simple magnification optical system is used in reproduction of a recording medium in which a large number of minute modified regions are three-dimensionally formed inside solid matter, contrast is insufficient and interlayer crosstalk is increased, and therefore, it is impossible to take a sufficient S/N ratio. Provided is a recording medium in which at least one layer is configured by a set of two adjacent sub-layers, and dots on a sub-layer correspond to a recording data ‘1’ and dots on the other sub-layer correspond to ‘0’. These data are played back.