Provided are an organic light emitting display device which can be simultaneously used as a mirror and a display screen in an external display device such as a mobile phone, and a manufacturing method for the organic light emitting display device. In one embodiment, an organic light emitting display device includes a first substrate and first transistors formed on the first substrate. A first organic light emitting diode is electrically connected to each of the first transistors. A second substrate is disposed opposite to the first substrate. Second organic light emitting diodes are formed on the second substrate. In the organic light emitting display device, a cathode electrode of each of the second organic light emitting diodes is formed of a reflective material.