A liquid crystal display device and a driving method thereof are provided which can increase a display grade by removing a DC residual image. The liquid crystal display device comprises: a liquid crystal display panel for displaying gray levels by a potential difference between a common electrode for applying a common voltage and pixel electrodes for applying data voltages; a common voltage regulating circuit for generating a variable common voltage which is longitudinally symmetrical with respect to a DC common voltage of a predetermined level and whose voltage level is stepwisely varied at predetermined intervals; and a black gamma reference voltage regulating circuit for adding the variable common voltage to an offset voltage set as a gamma reference voltage of a black gray level to generate a variable gamma reference voltage varying with respect to the gamma reference voltage of the black gray level, the variable gamma reference voltage of the black gray level being varied in synchronization with the variable common voltage.