PURPOSE: To form an ink jet print head having uniform and high printing quality insusceptible of an operation method by providing a closing cover at a chip at a side facing an ink reservoir tank.

CONSTITUTION: A closing cover 1 is provided to a chip 11 at a side facing an ink reservoir tank 12 and the cover 1 has an opening 8 at an intersection between an ink channel 16 and a supply channel 15. The size of the cross section of the opening 2 is accurately equal to that of the cross section obtained by the intersection between the channels 16, 15. The longitudinal section of the channel 16 is in a trapezoidal shape and a sharp section in the trapezoidal shape is connected to the channel 15. A pressure wave due to an ink evaporation bubble which is generated when a heating resistor is driven is firstly propagated to a circumference of an outlet opening 10 then to the separated channel 15 in the dynamic change. When the pressure wave reaches the circumference of the channel 15, the ink is urged to move back from the channel 16 to the channel 15 by virtue of the rebound phenomenon. When the pressure is attenuated, the ink is sucked into the channel 16 by the capillary phenomenon of the channel 16.