PURPOSE: To improve the thermal efficiency by stacking and bonding a plate material formed with a plurality or grooves on the inner surface, a partition plate, a heater and a base plate formed with an electrode on the inner surface, and further opening a hole at the partition plate and directly contacting the heater with ink in an orifice.

CONSTITUTION: A plate material 4 formed with grooves 8 and a partition plate 5 are bonded to form an orifice 7. Since the plate 5 can be interposed between the material 4 and a base plate 6, thermal conductivity can be preferentially reduced in thickness, thereby rapidly transmitting the heat of the heater to ink in the orifice. Further, a hole 10 is formed at the plate 5, thereby directing contacting the heater 12 with the ink in the orifice. Thus, the thermal conduction can be further accelerated to eliminate the removal of the heat from the ink in the adjacent orifice, thereby enhancing the thermal efficiency.