A transparent organic light emitting display device comprising: a first substrate (110A, 110B, 110C, 110D, 210A, 210C, 210D, 210E, 210F, 310A, 310B, 310C, 510) having a plurality of sub pixel regions, each of the plurality of sub pixel regions having an emissive area and a transmissive area where external light can pass through; a thin film transistor disposed in the emissive area; an organic light emitting element (140A, 140C, 140D, 240A, 240F, 340A, 540) disposed in the emissive area, the organic light emitting element being electrically connected to the TFT disposed in the emissive area; and a plurality of insulating layers (115C, 115D, 131B, 132A, 133A, 134A, 134B, 134C, 134D, 132D, 160C, 160D, 215A, 215C, 215D, 215E, 215F, 231C, 231E, 232F, 233A, 233F, 234C, 234A, 234D, 234E, 234F, 237D, 260A, 260C, 260D, 260E, 260F, 315A, 315B, 315C, 331A, 331C, 333B, 333C, 334A, 334B, 334C, 360B, 360C, 515, 531, 532, 533, 534, 538, 539, 560) in the emissive area, wherein at least a part of at least one of the plurality of insulating layers is extended into the transmissive area and the difference of refractive index between the first substrate and said at least a part, which is extended into the transmissive area, is equal to or less than 0.1, wherein the plurality of insulating layers comprise a first insulating layer on the first substrate, a second insulating layer, and a third insulating layer disposed on the TFT, the TFT is disposed on the first insulating layer and has a gate electrode, the second insulating layer, a source electrode, a drain electrode and an active layer, the organic light emitting element is disposed on the second insulating layer, an encapsulation layer is disposed on the organic light emitting element, and at least one of the first, second and third insulating layers has a refractive index that differs from a refractive index of the first substrate by more than 0.1, and is only contained within the emissive area of the sub pixel region a first substrate (110A, 110B, 110C, 110D, 210A, 210C, 210D, 210E, 210F, 310A, 310B, 310C, 510) having a plurality of sub pixel regions, each of the plurality of sub pixel regions having an emissive area and a transmissive area where external light can pass through; a thin film transistor disposed in the emissive area; an organic light emitting element (140A, 140C, 140D, 240A, 240F, 340A, 540) disposed in the emissive area, the organic light emitting element being electrically connected to the TFT disposed in the emissive area; and a plurality of insulating layers (115C, 115D, 131B, 132A, 133A, 134A, 134B, 134C, 134D, 132D, 160C, 160D, 215A, 215C, 215D, 215E, 215F, 231C, 231E, 232F, 233A, 233F, 234C, 234A, 234D, 234E, 234F, 237D, 260A, 260C, 260D, 260E, 260F, 315A, 315B, 315C, 331A, 331C, 333B, 333C, 334A, 334B, 334C, 360B, 360C, 515, 531, 532, 533, 534, 538, 539, 560) in the emissive area, wherein at least a part of at least one of the plurality of insulating layers is extended into the transmissive area and the difference of refractive index between the first substrate and said at least a part, which is extended into the transmissive area, is equal to or less than 0.1, wherein the plurality of insulating layers comprise a first insulating layer on the first substrate, a second insulating layer, and a third insulating layer disposed on the TFT, the TFT is disposed on the first insulating layer and has a gate electrode, the second insulating layer, a source electrode, a drain electrode and an active layer, the organic light emitting element is disposed on the second insulating layer, an encapsulation layer is disposed on the organic light emitting element, and at least one of the first, second and third insulating layers has a refractive index that differs from a refractive index of the first substrate by more than 0.1, and is only contained within the emissive area of the sub pixel region