A circuit board includes: a substrate; source and drain electrodes formed on the substrate; an organic semiconductor layer formed on the source and drain electrodes; a gate insulating layer formed on the organic semiconductor layer; and a gate electrode formed on the gate insulating layer, wherein: the substrate includes a first part, a second part, and a third part interposed between the first and second parts and a thickness of the first part or a thickness of the second part is greater than that of the third part; the source electrode is formed on the first part; the drain electrode is formed on the second part; a part of the organic semiconductor layer is formed on the third part; and a thickness of the gate insulating layer disposed on the first and second parts is smaller than that of the gate insulating layer disposed on the third part.