An active matrix liquid crystal display device and driving method thereof is provided, in which two different gamma voltage signals can be generated for two pixels of a sub-pixel without extra source lines or gate lines. In a sub-pixel having a first pixel and a second pixel, the switching on/off of the first pixel is controlled by one gate line and that of the second pixel is controlled by one gate line and one source line. The first pixel has a first thin film transistor (TFT) and an electrostatic capacitor. The second pixel has second and third TFTs serially connected. Gate electrodes of the two serially-connected TFTs are connected to the gate line and the source line, respectively.