There is provided a first die in which a plurality of projections are arrayed in a first direction with a fixed pitch. Each projection is elongated in a second direction perpendicular to the first direction. The first die faces a first face of a plate member. A second die is opposed to the first die while supporting a second face of the plate member. At least one dam member is provided in at least one of the first die and the second die, so as to project from one of the first die and the second die toward the other. The first and second dies are approached so that the dam member is dug into at least one of the first face and the second face. The first and second dies are further approached so that the projections are dug into a first region in the first face, thereby forming partitioned recesses to be pressure generating chambers of a liquid ejection head. The dam member is situated in the vicinity of at least one of ends in the first direction of the first region, thereby suppressing a plastic flow of the material in the first direction caused by the dug projections.