Provided is an organic light emitting display device including a base substrate, a pixel layer, a quantum dot layer, and a thin film encapsulation part. The pixel layer includes a plurality of organic light emitting diodes on the base substrate. The quantum dot layer includes quantum dots on the pixel layer. The thin film encapsulation part is between the quantum dot layer and the pixel layer, and seals the pixel layer. The thin film encapsulation part includes a first inorganic film and an organic film. The first inorganic film has a plurality of first auxiliary films, each having a first refractive index, and a plurality of second auxiliary films, each having a second refractive index that differs from the first refractive index, alternately stacked with the plurality of first auxiliary films along a thickness direction of the base substrate.