A display device including a display layer displaying a black or white color according to an applied voltage, a transparent and non-transparent electrode that are disposed to sandwich the display layer, and a TFT driving circuit capable of applying any given voltage between the pair of electrodes. Also provided is a connection destination switching switch capable of switching the connection destination of the entire transparent electrode to an earth terminal or a connector power source terminal of an external power source connector. With this configuration, a voltage can be applied between the pair of electrodes without using the TFT driving circuit. Accordingly, if the TFT driving circuit fails to operate due to trouble caused by the displaying of information which is not permitted to be shown to others, a voltage can be applied to the display layer so that the displayed information can be erased.