preparing a substrate including a heating resistor and a cavitation resistant film including a portion provided at a position where the heating resistor is covered, a surface of the portion being exposed to an outside;

forming a protective film covering the surface of the portion of the cavitation resistant film with a metallic material containing at least one of titanium, tungsten, and titanium-tungsten;

etching the substrate after forming the protective film; and

removing the protective film after the etching.