An ink jet head circuit board is provided which has heaters to generate thermal energy for ink ejection as they are energized. This circuit board reduces areas of the heaters to achieve higher printing resolution and image quality. This board also prevents a degradation of thermal energy efficiency and reduces power consumption. The protective insulation layer for the electrode wire layer is formed of two layers and one of the two layers is removed from above the heater to improve the heat energy efficiency. The resistor layer is deposited over the electrode wire layer. The patterning for removing the protective insulation layer is done in a wider range than a gap of the electrode wire layer, the gap being used to form the heater. Further, by forming the electrode wires in two layers, a possible reduction in an effective bubble generation area of the heater can be prevented.