An ink jet head circuit board is provided which has heaters to generate thermal energy for ink ejection. This board has the heaters formed with high precision to reduce their areas. It has provisions to protect the electrode wires against corrosion and prevent a progress of corrosion. The substrate is deposited with the thin first electrodes made of a corrosion resistant metal. Over the first electrodes the second electrodes made of aluminum are formed. The second electrodes are deposited with a resistor layer. The heater is formed in the gap between the first electrodes. With this construction, the heaters are formed without large dimensional variations among them. Should a defect occur in a protective layer above or near the heaters, a progress of corrosion can effectively be prevented because the material of the resistor layer is more resistant to encroachment than aluminum and the first electrodes are corrosion resistant.