Undesirable deflection of partitioning walls between ink pressure chambers is prevented during ink discharge operations even when the partitioning walls are made very thin to achieve a high density inkjet head. The diaphragms of the discharge nozzles of the inkjet head as well as the diaphragms of the non-discharge nozzles are all driven to contact the corresponding individual electrodes, and this diaphragm to individual electrode contact state is maintained in the non-discharge nozzles while the diaphragms of the discharge nozzles are released from individual electrodes to discharge ink. After printing is completed the diaphragms of the non-discharge nozzles are slowly released from the corresponding individual electrodes at a speed that will not cause undesirable ink discharge. By thus maintaining low compliance in the ink pressure chambers of the non-discharge nozzles, deformation of the partitioning walls between discharge and non-discharge nozzles due to change in the ink pressure can be reliably prevented. A drop in ink discharge performance due to such partitioning wall deformation can be reliably prevented, and printing with high resolution, precise print quality can be easily achieved.