A method for manufacturing a substrate for a liquid discharge head provided with a silicon substrate and a supply port, including: providing the silicon substrate having an insulating layer on a first surface and an etching mask layer having a plurality of apertures on a second surface which is a rear surface of the first surface, wherein the insulating layer is provided in a region ranging from a position opposing the apertures to a position opposing a portion between the adjacent apertures of the mask layer; and forming holes by etching a silicon part of the silicon substrate so that an etched region reaches a portion of the insulating layer opposing the apertures, wherein the silicon wall provided between the adjacent holes is etched so that the portion in the first surface side thereof can be thinner than the portion in the second surface side thereof.