To provide a display device permitting to reduce power consumption of the entire device by reducing consumption current due to charge/discharge of, especially, signal lines, and to provide a portable terminal device using the same.

In a liquid crystal display device mounted with memory built-in pixels, each pixel circuit 11 is provided with a pixel selection switch 24 permitting to write a picture data to a memory circuit 23 synchronizing with horizontal scanning so as to be able to control writing of the picture data to the memory circuit 23 in pixel units and hold the previous data in the memory circuit 23 as it is, without rewriting data to those pixels for which rewriting of memory data is not necessary.