A liquid crystal display device has a liquid crystal panel, a DA converter for generating a common electrode signal to be applied to a common electrode of a liquid crystal, and a non-volatile memory for encoding an optimum value of the common electrode signal into an ID code and storing the ID code therein. The DA converter generates the optimum common electrode signal corresponding to the ID code read out from the non-volatile memory. A liquid crystal panel manufacturer ships the liquid crystal panel in which the optimum value of the common electrode signal is encoded into the ID code and stored in the non-volatile memory in an inspecting process. The assembling manufacturer using the liquid crystal panel can easily set the optimum value of the common electrode signal. Furthermore, the liquid crystal display device has a CPU decoding the ID code read out from the non-volatile memory. Alternatively, it is possible to supply a data of a value of the common electrode signal to a user of the liquid crystal. The user adjusts the common electrode signal generating circuit by using the data of the value of the common electrode signal.