An OLED display device includes a substrate. A first electrode is disposed on the substrate. An organic light emitting layer is disposed on the first electrode. A second electrode is disposed on the organic light emitting layer. A thin film encapsulation layer is disposed on the second electrode. The thin film encapsulation layer includes at least one inorganic layer and at least one organic layer that is disposed alternately with the at least one inorganic layer. The at least one organic layer includes a low refractive index layer overlapping the organic light emitting layer and a high refractive index layer disposed on the low refractive index layer. The high refractive index layer includes a convex surface protruding toward the organic light emitting layer.