By manipulating a relative potential relationship of potentials by voltages applied to selected electrodes, nonselected electrodes and an opposed electrode 20 among a plurality of record electrodes 13a through 13z installed at vicinities of an opening portion 11 of a head, ink is injected, printing of high resolution is made possible and by using a dispersing type ink and changing polarities of the voltages applied to the opposed electrode 20 and the record electrodes, density of injected ink is made variable.