A liquid ejection head substrate includes a base layer, a heating resistance element provided over the base layer to generate a heat energy for ejecting a liquid, a first insulation layer covering the heating resistance element, and a protective layer having, on the first insulation layer, a first region which overlaps the heating resistance element via the first insulation layer and a second region which does not overlap the heating resistance element and formed of a material including a metal which is eluted by an electrochemical reaction. The liquid ejection head substrate further includes a second insulation layer provided over a region overlying the base layer and not provided with the protective layer and over the second region of the protective layer.