A liquid crystal display device includes a sound output function. A sound output function can be added to a liquid crystal device having a light source while preventing any increase in the external size of the liquid crystal display device. The liquid crystal display device includes a liquid crystal layer sandwiched between a first substrate and a second substrate which oppose each other, a flexible printed circuit (FPC) connected to a brim portion of the second substrate, a light guide plate, and an LED. An excitation source is arranged at a portion corresponding to the back side of the FPC connection portion on the second substrate. The excitation source deflects and vibrates the second substrate of the liquid crystal display panel according to a sound signal from an outside source. That is, the second substrate is used as a vibration plate for the output of a sound. The liquid crystal display device can preferably be used for a liquid crystal module used in mobile devices such as a mobile telephone and a PDA.