PURPOSE: To obtain an image print with a high resolution without causing a loading by supplying an ink drop jetting apparatus with an ink having the viscosity near the saturation point in the saturation area where the ink drop diameter is kept constant regardless of the ink viscosity.

CONSTITUTION: For example, a unimorph type piezo-electric vibrator 2 with the diameter D=10mm in which a metal plate is glued on a lead titanate zirconate based piezo-electric ceramic plate is mounted at the large-diameter end of a horn-shaped pressure displacement chamber 3 to give the vibration diameter D'=8mm. A diaphragm 4 made of stainless steel or the like with a thickness of δ=30μm is fastened at the short diameter end with an opening diameter d=2mm of the pressure displacement chamber 3 in such a manner as to free to vibrate and on orifice plate 7 with an orifice 6 of 50μm made at the center thereof to form an ink chamber 5 with a thickness Δ=400μm. An ink drop jetting apparatus 1 is supplied with an ink having the viscosity of 5W14cps in an saturation area to jet a uniform ink drop with an attached area of 2×10-2mm2.