An organic light emitting display device includes: a display unit including a plurality of pixels each coupled to a first scan line, a second scan line, and a data line; a scan driver configured to supply, to the display unit, a plurality of first scan pulses corresponding to a bias period and a second scan pulse corresponding to a data write period after the bias period through the respective first and second scan lines; an emission driver configured to supply an emission control signal to the display unit through emission control lines; a data driver configured to supply a data voltage to the display unit through the data lines; and a power supply configured to commonly supply, to the pixels, an initialization voltage, the initialization voltage having a voltage level switching between a first voltage level and a second voltage level in a preset period.