An ink jet print head is provided which can improve throughput by increasing an ink ejection frequency and prevent crosstalk among a plurality of heat application portions, realizing a capability of printing high-quality images at high speed. An opening size of the supply ports in a direction perpendicular to the array direction of the heat application portions is made greater than the length in the direction of electrothermal conversion elements. The supply ports are arranged along the array direction so that they adjoin the heat application portions in the array direction.