The present invention provides a method of manufacturing a thin film transistor of a top-contact structure with suppressed deterioration by a process which is easy and suitable for increase in area without damaging an organic semiconductor pattern. The organic semiconductor pattern is formed on a substrate. An electrode material film is formed on the substrate so as to cover the organic semiconductor pattern. A resist pattern is formed on the electrode material film. By wet etching using the resist pattern as a mask, the electrode material film is patterned. By the process, a source electrode and a drain electrode are formed.