A display device includes: an image display panel including pixels each including a first to a forth sub-pixel that display a first color to a fourth color; and a signal processing unit. The signal processing unit stores an expanded color space, determines maximum set brightness as an upper limit value of brightness displayable within a range of the brightness in the expanded color space so that the maximum set brightness increases as a panel average input value decreases, determines an input expansion coefficient for expanding the color displayed by the image display panel to a color of the maximum set brightness, obtains the output signal of the first to forth sub-pixel based on the input signal of the first to third sub-pixel and the input expansion coefficient. The expanded color space is a color space that can extend a color of brightness higher than that in a standard color space.