A method for manufacturing a plurality of ink-jet heads comprising: forming an insulating ceramic layer at least on one of outermost metal plates of a plurality of metal plates, the outermost metal plates forming outermost layers of a laminate, the plurality of metal plates forming a metal plate set; stacking a plurality of metal plate sets via the insulating ceramic layer of each set; and heating the stacked plurality of metal plate sets and simultaneously diffusion bonding the plurality of metal plates in each set of the plurality of metal plate sets. A plurality of laminates can be manufactured at once by diffusion bonding the metal plates of the plurality of metal plate sets all together, without any diffusion bonding between two metal plates respectively belonging to different metal plate sets.