PURPOSE: To emit a stable liquid droplet between nozzles by providing a porous member composed of a polymer material of a hydrophobic-hydrophilic copolymer to the inner wall of a common ink sump on the side of an ink supply passage.

CONSTITUTION: The pressure wave generated in a pressure chamber 2 propagates in the direction of an ink emitting orifice 1 as ink emitting energy and also propagates in the direction of an ink sump 5 through an ink supply passage 3. However, since the pressure wave propagating in the direction of the ink sump 5 is absorbed and attenuated by the porous member 4 provided to the inner wall of the ink sump 5 on the side of the ink supply passage 3, said pressure wave does not propagate to the ink sump 5 and does not also again propagate to the pressure chamber 2. Herein, the porous member 4 is constituted of a polymer material composed of a hydrophobic-hydrophilic copolymer and the polymer material is composed of a acrylonitrile/vinyl alcohol copolymer, an ethylene/vinyl alcohol copolymer or a vinyl chloride/vinyl alcohol copolymer.