An organic light emitting display device having high transmittance with respect to external light and a method of manufacturing the same. The organic light emitting display device includes a substrate; a plurality of pixels formed on the substrate, each of the pixels including a first region that emits light and a second region that transmits external light; a plurality of thin film transistors disposed in the first region of each pixel; a plurality of first electrodes disposed in the first region of each pixel and electrically connected to the thin film transistors, respectively; a second electrode formed opposite to the plurality of first electrodes and comprising a plurality of transmission windows corresponding to the second regions; and an organic layer formed between the first electrodes and the second electrode. The transmission windows can be formed in the second electrode, that is, a cathode.