An organic light-emitting display device can include a display panel that expresses luminance based on a driving current corresponding to a data voltage and a first power; a control circuit that outputs a first mode control signal for a normal mode and a second mode control signal for a standby mode for lower luminance; and a power source that supplies the first power at a first voltage level, in response to receiving the first mode control signal, and supplies the first power at a second voltage level that is lower than the first voltage level, in response to receiving the second mode control signal.