A structure forming method according to an aspect is a structure forming method for forming a first hole and a second hole having width smaller than width of the first hole in a substrate with dry etching and forming a structure. The structure forming method includes forming an etching mask on the substrate, etching a portion of the etching mask overlapping a first hole forming region where the first hole is formed, etching a portion of the etching mask overlapping a second hole forming region where the second hole is formed, and performing the dry etching of the substrate using the etching mask as a mask.