A display device includes a gate scanning circuit and a driver IC. The driver IC includes a voltage detection circuit for detecting a voltage level of an external power supply, a voltage generation circuit for generating the voltage for driving the gate line, a switching circuit for switching between the output voltage of the voltage generation circuit and the voltage of the external power supply, and a drive circuit. Upon detection of the voltage outside of the predetermined voltage range by the voltage detection circuit, the switching circuit supplies the voltage of the external power supply to the gate scanning circuit. The gate scanning circuit selects all gate lines for outputting the voltage of the external power supply. The drive circuit supplies the GND level to all the source lines.