In order to provide an optical element in which the occurrence of a region where no light beams are present (omission) is prevented, an optical element is provided with a main substrate which is manufactured from a light-transmitting material and in which a front surface and a rear surface are parallel to the setting directions, wherein at least one main beam splitter surface is provided obliquely to the setting directions and formed inside the primary substrate. The optical element is also provided with a sub substrate which is manufactured from a light transmitting material and in which a front surface and a rear surface are parallel to the setting directions, wherein a sub beam splitter surface is arranged at least between the front surface or the rear surface of the single sub substrate, and the rear surface or the front surface of the main substrate.