A display device includes a first display unit emitting an output light having an output spectrum corresponding to a highest gray level of the display device, wherein an intensity integral of the output spectrum from 494 nm to 575 nm is defined as a first intensity integral, an intensity integral of the output spectrum from 380 nm to 493 nm is defined as a second intensity integral, an intensity integral of the output spectrum from 576 nm to 780 nm is defined as a third intensity integral, a summation of the second intensity integral and third intensity integral is defined as a first summation, a ratio of the first summation to the first intensity integral is defined as a first ratio, and the first ratio is greater than 0.0% and less than or equal to 37.0%.