To provide a device which is free from any loss in converting the expansion/ contraction of a piezoelectric element into the vibration in the thickness direction, and in which the dripping condition is not disturbed by the differential pressure between an emitter and a pressure chamber.

The pressure fluctuation in an emitter 11 can be directly generated by the expansion/contraction of a piezoelectric element 1 to efficiently emit the drip 17 by providing an emitter 11 which is provided with an orifice plate 15 on a lower part and whose inside is hollow, a case 3 which is arranged on an upper part in the emitter 11 and provided with a downward recessed part, a clamp member 2 arranged at a lower end of the case 3, and the flat-plate shaped piezoelectric element 1 whose end part is held between two seal sliding members 2b of the clamp member 2 to form a pressure chamber in the recessed part of the case 3, and which is expanded/ contracted by a driving power source 10. Since an air intake flow rate regulating valve provided on an intake pipe to be communicated with the pressure chamber, and a control device to control the air intake flow rate regulating valve are provided, the pressure in the pressure chamber is adjusted so as to be always equal to the pressure in the emitter, and expansion/contraction of the piezoelectric element becomes smooth to enable excellent emission of the drip.