An inkjet head comprising a nozzle, an ink passage in communication with the nozzle, a diaphragm provided at one part of the ink passage, and an electrode provided in opposition to the diaphragm whereby an electrical pulse is applied between the diaphragm and electrode to deform the diaphragm by means of electrostatic force, thereby ejecting ink droplets from the nozzle. The actuator contains at least a vibration chamber formed by the diaphragm and electrode, and is sealed or made airtight with the volume V so that the ratio between the actuator volume V and the volume .DELTA.V eliminated by a distortion of the diaphragm during ink-jet head drive is within the range 2.ltoreq.V/.DELTA.V.ltoreq.8.