A method for producing a liquid-discharge-head substrate includes a step of preparing a silicon substrate including, at a front-surface side of the silicon substrate, an energy generating element; a step of forming a first etchant introduction hole on the front-surface side of the silicon substrate; a step of supplying a first etchant into the first etchant introduction hole formed on the front-surface side of the silicon substrate, and supplying a second etchant to a back-surface side of the silicon substrate; a step of stopping the supply of the second etchant; and a step of, after the supply of the second etchant has been stopped, forming a liquid supply port extending through front and back surfaces of the silicon substrate by the supply of the first etchant.