An etching method includes preparing a compound; and etching an etching target in an environment in which the compound is present. The etching of the etching target includes: etching the etching target in an environment in which hydrogen (H) and fluorine (F) are present when the etching target contains silicon nitride (SiN); and etching the etching target in an environment in which nitrogen (N), hydrogen (H) and fluorine (F) are present when the etching target contains silicon (Si). The compound contains an element that forms an anion of an acid stronger than hydrogen fluoride (HF) or contains an element that forms a cation of a base stronger than ammonia (NH3).