A stereoscopic image display device, including a display unit comprising a plurality of pixel units, wherein at least one of the pixel units has a short side extended in a first direction and a long side extended in a second direction different from the first direction, and an image conversion unit comprising a lenticular lens overlapped with at least two of the pixel units arranged in the first direction, wherein the lenticular lens is extended in the second direction and a first prism corresponding to the lenticular lens is arranged in the second direction.