An organic thin film transistor substrate includes a gate line formed on a substrate, a data line intersecting the gate line and defining a subpixel area, an organic thin film transistor including a gate electrode connected to the gate line, a source electrode connected to the data line, a drain electrode facing the source electrode, and an organic semiconductor layer forming a channel between the source and drain electrodes, a passivation layer parallel with the gate line, for covering the organic semiconductor layer and peripheral regions of the organic semiconductor layer, and a bank insulating layer for determining the position of the organic semiconductor layer and the passivation layer.