Abstract: An etching method includes: providing, to an interior of a chamber, a substrate having a three-layered film formed by stacking a first silicon oxide-based film, a silicon nitride-based film, and a second silicon oxide-based film; and collectively etching the three-layered film using a HF—NH3-based gas in the interior of the chamber while adjusting a gas ratio in each of the first silicon oxide-based film, the silicon nitride-based film, and the second silicon oxide-based film.