An element substrate including a base having a heat-generating resistor element which generates thermal energy used for discharging a liquid; an electrically conductive protective layer covering the heat-generating resistor element; an insulating layer provided between the heat-generating resistor element and the protective layer; and a potential applying unit for applying a potential to the protective layer such that a potential of the protective layer is lower than a potential at one end of the heat-generating resistor element and higher than a potential at the other end of the heat-generating resistor element with a voltage being applied between the one end and the other end of the heat-generating resistor element.