An organic thin film transistor comprising an organic semiconductor layer that does not cause a coffee stain effect and can prevent an imperfect contact with source and drain electrodes, and a flat panel display apparatus comprising the organic thin film transistor are provided. The organic thin film transistor comprises a gate electrode; source and drain electrodes insulated from the gate electrode; and an organic semiconductor layer insulated from the gate electrode and contacts the source and drain electrodes, wherein the organic semiconductor layer has a circular shape when viewed through a substrate on which the organic thin film transistor is formed, and an edge portion of at least one of the source and drain electrodes contacting the organic semiconductor layer having a curved shape that is concave toward the organic semiconductor layer.