An organic semiconductor device with a vertical structure having both functions of an organic thin film transistor and light-emitting element, where the electrical characteristics as both the organic thin film transistor and light-emitting element can be controlled in the case of forming a gate electrode with an organic conductive film, and a manufacturing method thereof. The above organic semiconductor device has such a structure that organic semiconductor films are sandwiched between a pair of electrodes functioning as a source electrode and drain electrode of an organic thin film transistor and also functioning as an anode and cathode of a light-emitting element, a thin organic conductive film functioning as a gate electrode is sandwiched between the organic semiconductor films, and a part of the organic conductive film is electrically connected to an auxiliary electrode, thereby the electrical characteristics as both the organic thin film transistor and light-emitting element can be controlled.