A method of producing an organic transistor which can form directly an organic semiconductor layer in pattern by simple processes and can produce an organic transistor excellent in transistor characteristics. The method includes: forming a hydrophobic/hydrophilic pattern substrate, in which a hydrophobic/hydrophilic pattern substrate is formed by using a hydrophobic substrate and by forming the hydrophilic region in pattern on the hydrophobic surface; forming a lyophilic functional layer, in which a lyophilic functional layer, made of an insulating functional material having the predetermined characteristics and having higher lyophilic properties to an organic solvent than that of the hydrophobic region, is formed on the hydrophilic region; forming an organic semiconductor layer, in which an organic semiconductor layer is formed on the lyophilic functional layer by selectively coating a coating solution for forming an organic semiconductor layer, which has an organic semiconductor material and an organic solvent, to the lyophilic functional layer.