PURPOSE: To improve the quality of a recording medium with sandwich structure by providing a thick plate of light transmission having a thicker thickness than the depth of focus of light irradiated to one recording layer to a stretched boundary of opposed recording layers and shifting the recording film of two discs respectively from each focus to separate optically the opposed recording layers.

CONSTITUTION: The sandwich optical disc is constituted by bonding two single board discs 8 so that the recording layers are opposed. As a boundary layer 7, a light transmission material such as plastic plate, glass plate or UV resin (ultraviolet curing resin) is used and when the focus of light is matched to record/reproduce a signal on one recording layer, complete OFF Focus is attained on the recording film of the other disc to eliminate effect on the other. That is, as the boundary layer 7, an optical thickness thicker than the depth of focus of the light irradiated on the recording layer 6 is provided and the thickness is in general ≥20W30μm. The single board discs 8 are bonded by a proper adhesives so that the recording layers 6 are opposed to both sides of the boundary layer 7.