A method of manufacturing an inkjet head at a low cost is provided. The inkjet head has a passage unit. A plurality of plates are laminated together to form the passage unit. The passage unit has individual ink passages that extend in the plate laminating direction. When the passage unit is to be manufactured, communication holes that will become individual ink passages later will first be formed in the plurality of plates that form the passage unit. All of the plates in which the communication holes are formed will be laminated together with a thermosetting adhesive. The laminated plates will be heated and pressure will be applied thereto. In this way, all of the plates will be simultaneously adhered. An ink passage unit can be manufactured in one adhesion step. The manufacturing costs of the ink passage unit can be reduced. Components such as actuator units, an ink supply unit, and the like will be attached to the manufactured ink passage unit to complete an inkjet head. An inkjet head can be manufactured at a low cost.