A process for producing a liquid ejection head including a silicon substrate having a supply port to supply a liquid to a flow path, and an ejection-orifice-forming member forming the flow path between the ejection-orifice-forming member and the silicon substrate and having an ejection orifice to eject the liquid in the flow path. The process includes forming an etching protection film so as to cover the ejection-orifice-forming member; forming the supply port passing through the silicon substrate by anisotropic etching using an alkaline aqueous solution; and removing the etching protection film. The etching protection film includes an organic polymer material having a storage modulus at 80° C. of 1.0×106 Pa or higher.