A substrate for a liquid ejection head, including: forming a sacrifice layer on a first surface of a silicon substrate in a region in which a liquid supply port is to open, the sacrifice layer containing aluminum which is selectively etched with respect to the silicon substrate; forming an etching mask on a second surface which is a rear surface of the first surface of the silicon substrate, the etching mask having an opening corresponding to the sacrifice layer; a first etching step of etching the silicon substrate by using the etching mask as a mask and by using a first etchant containing 8 mass % or more and less than 15 mass % of tetramethylammonium hydroxide; and after the first etching step, a second etching step of removing the sacrifice layer by using a second etchant containing 15 mass % or more and 25 mass % or less of tetramethylammonium hydroxide.