To extend a driving time by charging a battery by using lighting of a display device.

An information terminal device 2 with a built-in self-feeding device 22 is provided with a liquid crystal display device 6, and the liquid crystal display device 6 uses a cold cathode-ray tube 12 as a back-light and is lighted with it from behind. A solar battery 16 is arranged in the neighborhood of this cold cathode-ray tube 12, and is configured to generate electricity by receiving the light from the cold cathode-ray tube 12. The electric power generated by the solar battery 16 is supplied to the battery 26 as a power source of the information terminal device 2 and changes the battery 26. Therefore, it is possible to make use of the lighting for the display device, which has partly been wasted before, and extend a driving time of the battery 26.