The method of driving a liquid crystal display device includes calculating a brightness average value of pixel data of at least one frame period supplied to a liquid crystal display panel, and storing the average to a memory unit; generating a brightness control signal having a duty ratio according to the brightness average value of the pixel data adjusted taking variation of transmissivity with an angle of view into account in a white or black driving mode of the liquid crystal display panel; and supplying the brightness control signal to a light source unit.