A liquid crystal display device capable of improving reliability of a backlight unit is disclosed.The liquid crystal display device includes: a backlight dimming modulating unit configured to modulate an internal algorithm backlight dimming control signal using an external input algorithm backlight dimming control signal and to maintain a dimming duty equal to or wider than an allowable dimming range of a backlight unit; arithmetic unit configured to multiply the external input algorithm backlight dimming control signal by the modulated internal algorithm backlight dimming control signal and to output a final backlight dimming control signal; and a data modulating unit configured to modulate image data using the external input algorithm backlight dimming control signal corresponding to the modulated final backlight dimming control signal.