PURPOSE: To make the power of a heating element generating an air bubble constant by selectively correcting the pulse signal applied to the heating element on the basis of the vicinal state of the heating element.

CONSTITUTION: A heating element 46 is connected across constant voltage VB and the drain of a drive transistor 58. By knowing the voltage drop between the constant voltage VB and both terminals of the heating element 46, desirable drain voltage is calculated. A comparator 62 compares actual drain voltage Vd with desired drain voltage VEXT and outputs the difference signal based on the voltage difference between Vd as VEXT to a converging circuit 70 along a line 64. The converging circuit 70 outputs one of a plurality of pulse signals VREF to a drive transistor 58 along a line 72 and receives the difference signal from the comparator 62 to send a pulse signal VREF to the gate of the drive transistor 58 along a line 72. The selected pulse signal is repeatedly outputted along the line 72 to turn the heating element 46 on and off and an ink drop is ejected from an ejector.