An organic light-emitting display device includes a gate electrode, a source electrode, and a drain electrode on a substrate, a gate interconnection line connected to the gate electrode, a source and drain interconnection line connected to the source and drain electrodes, a first test pad electrically connected to the source and drain interconnection line, and a second test pad electrically connected to the gate interconnection line. The second test pad is at a same level as the first test pad, and the gate electrode is on a different layer than the source and drain electrodes.