A display device includes a display unit emitting an output light that has an output spectrum corresponding to a highest gray level of the display device. A maximum peak of the output spectrum between 380 nm and 493 nm is defined as a first intensity peak. A secondary peak of the output spectrum between 380 nm and 493 nm is defined as a second intensity peak. A first sub-peak ratio of the second intensity peak to the first intensity peak is in a range from 7.0% to 75.0%.