An organic light emitting display device in an embodiment of the present invention comprises a display panel equipped with a plurality of pixels each including an OLED and a driving TFT for driving the OLED and a sensing circuit connected to pixels through a sensing line and detecting driving characteristics of a corresponding pixel. The sensing circuit may comprise a plural sensing units including an integrator for integrating currents respectively flowing two adjacent sensing lines connected to inverting and non-inverting input terminals of a fully differential amplifier, a sampling unit for respectively sampling two integral outputs of the integrator and a scaler for regulating an operating range of outputs of the sampling unit, a differential amplifier for differentially amplifying one or more outputs of the scaler, and an ADC for converting an output of the differential amplifier into a digital sensing value.