An etching method of etching silicon formed on a side surface of a recess that exists in a substrate includes: forming an oxide film on a surface of the silicon by performing a radical oxidation processing on the substrate; performing a chemical processing with a gas on the oxide film; and removing a reaction product produced by the chemical processing, wherein the forming the oxide film includes: a first phase of performing a radical processing with a plasma of an oxygen-containing gas; and a second phase of performing a radical processing with a plasma of the oxygen-containing gas and an etching gas, and wherein the forming the oxide film, the performing the chemical processing, and the removing the reaction product are repeated multiple times.