An organic electronic element manufacturing method is a method of manufacturing an organic electronic element (1) having flexibility using a roll-to-roll process, including a first electrode forming step in which a first electrode (21) is pattern-formed onto a flexible substrate (10), a functional layer forming step in which a functional layer (23) containing an organic material is pattern-formed onto the first electrode (21), and a mask forming step in which a mask element (30) having flexibility is formed on the substrate (10) such that it has an opening on at least a portion of the functional layer (23) and at least a portion of the first electrode (21) with the functional layer (23) therebetween and covers edge portions (21a and 23a) on at least one side of the first electrode (21) and the functional layer (23).