A display device includes a display panel including a gate line and a data line, a gate driver that outputs a gate voltage to the gate line according to a gate output enable signal, a data driver that outputs a data voltage to the data line, a detecting circuit that detects a state of a clock signal. The state of the clock signal includes a normal or abnormal state. A masking circuit performs a masking operation for the gate output enable signal according to the state of the clock signal and a level of a reset signal, where the level of the reset signal includes a first or second level corresponding to a power-on or off of the display device, respectively.