A display device including a liquid crystal display (LCD) panel, a backlight module, and a photo-sensing device is provided. The backlight module is disposed below the LCD panel and is suitable for providing a light source. The photo-sensing device is built in the LCD panel and includes a plurality of photo-sensors having different illumination sensing capabilities. The backlight module modulates the output intensity of the light source according to the sensed result of one of the photo-sensors. Thereby, the display device can precisely modulate the intensity of the back light according to the intensity of ambient light so as to improve the contrast ratio and to reduce the power consumption.