Disclosed is a display device including: a substrate; and a first light-emitting element and a second light-emitting element over the substrate and adjacent to each other. The first light-emitting element and the second light-emitting element each possess a first electrode, an EL layer over the first electrode, a second electrode over the EL layer, and an optical adjustment layer over the second electrode. The optical adjustment layer over the first light-emitting element is different in refraction index from the optical adjustment layer over the second light-emitting element. A first material included in the optical adjustment layer may be the same in composition but different in chemical structure between before and after the light irradiation. Alternatively, the first material may be the same in composition but different in phase structure between before and after the light irradiation.