In one embodiment, there is provided a method of manufacturing an organic layer. The method includes: forming an organic material solution layer on a substrate; and heating, by a directional heat source assembly, at least a first portion of organic material solution of the organic material solution layer that is inside a to-be-treated area of the substrate, to increase an evaporation rate of the first portion of the organic material solution, whereby, reducing a thickness difference, due to different evaporation rates of the first portion of the organic material solution and a second portion of the organic material solution of the organic material solution layer that is outside the to-be-treated area of the substrate, of the organic layer that is cured from the organic material solution layer.