An OLED display device includes a substrate including a display region and a pad region, a display structure in the display region on the substrate, and a pad electrode structure in the pad region on the substrate, the pad electrode structure having a first pad electrode on the substrate, a first insulation layer covering opposite lateral portions of the first pad electrode and exposing a portion of an upper surface of the first pad electrode, a second pad electrode on the first pad electrode and on the first insulation layer, the second pad electrode having a step portion where the first pad electrode and the first insulation layer are overlapped, and a third pad electrode on the second pad electrode and on the first insulation layer, the third electrode covering the second pad electrode.