Provided are a light-emitting diode (LED) display device and a method of operating the LED display device determining whether a line flicker will occur based on a level of an input image signal, obtaining an LED line scan order corresponding to the level of the input image signal and brightness according to the input image signal based on the determining, and driving at least one LED line based on the LED line scan order. An LED line scan order may be adjusted according to a level of an input/output image signal in an LED display device so as to reduce occurrence of a line flicker phenomenon in all levels of the input/output image signal.