A driving method of an OLED display device having a plurality of pixels each including an OLED which emits light in response to pixel data, includes applying black data to the pixels during a predetermined period directly after system power is applied, supplying driving voltages to the OLEDs during initial driving where the black data is applied to the pixels, detecting a driving current flowing through the OLEDs by the black data at a first non-emission period after at least one frame has elapsed from a time point where the driving voltages are supplied to the OLEDs, and applying pixel data to the pixels for normal driving subsequent to the initial driving.