To provide a method for easily manufacturing an organic semiconductor element having an arbitrary shape.

A method for manufacturing an organic semiconductor element constituted of a gate insulating layer, a gate electrode, a source electrode, a drain electrode, and an organic semiconductor layer includes a process (1) for forming a conductive polymer antecedent monomer layer, a process (2) for holding the monomer layer at a prescribed temperature, and a process (3) for applying oxidizer solution to the desired position of the monomer layer to obtain a polymer layer with desired conductivity.