NOVELTY - The method involves arranging a substrate (S100) to a side of a reaction container. A free cursor is fixed (S110) on the substrate and made of copper and gallium. The container is sealed (S120) with rapid thermal process apparatus. The free cursor of the substrate is changed (S130) with a selenium plate. A light absorption layer is formed (S140) on a surface of the substrate. The container is heat-treated (S150) with selenium powder. A separable cover is fixed on a main body. The selenium powder is dissolved into solvent and selenium solution.    USE - Method for manufacturing a light absorption layer of a thin film solar cell.    ADVANTAGE - The method enables mixing the selenium powder and sulfur into a sodium source by using an element selenium powder so as to reduce consumption of selenium, so that fabrication cost of the light absorption layer can be reduced. The method enables reducing selenization thermal processing annealing time and external contamination by maintaining selenization halfway reaction container in nitrogen atmosphere. The method enables facilitating modulation of a supply unit by uniformly supplying selenium, sodium and sulfur to a selenium feeder, so that manufacturing process of the light absorption layer can be improved. The method enables saving safety equipment installation expense by using poisonous gas, so that waste of unnecessary selenium is decreased.    DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart illustrating a method for manufacturing a light absorption layer of a thin film solar cell. '(Drawing includes non-English language text)'    Step for arranging substrate to side of reaction container (S100)    Step for fixing free cursor on substrate (S110)    Step for sealing container with rapid thermal process apparatus (S120)    Step for changing free cursor of substrate (S130)    Step for forming light absorption layer on surface of substrate (S140)    Step for heat-treating container with selenium powder (S150)