According to an embodiment, a wafer W includes a layer EL to be etched, an organic film OL, an antireflection film AL, and a mask MK1, and a method MT according to an embodiment includes a step of performing an etching process on the antireflection film AL by using the mask MK1 with plasma generated in a processing container 12, in the processing container 12 of a plasma processing apparatus 10 in which the wafer W is accommodated, and the step includes steps ST3a to ST4 of conformally forming a protective film SX on the surface of the mask MK1, and steps ST6a to ST7 of etching the antireflection film AL by removing the antireflection film AL for each atomic layer by using the mask MK1 on which the protective film SX is formed.