The organic light emitting display device comprises a display panel having a plurality of gate lines and data lines for defining a plurality of sub-pixels; an organic light emitting device in each sub-pixel; a driving thin film transistor in each sub-pixel; a plurality of reference voltage lines in the display panel to apply a reference voltage to the sub-pixels in the display panel; and a VSS electrode connected to the reference voltage lines in the one side of the display panel to apply a VSS voltage to the reference voltage lines.