A pulse generator forms, from setting data respectively stored in an ejection relevant waveform setting register and a first high impedance setting register, an ejection relevant driving pulse for setting an electrode of an ink chamber communicating with an ejection relevant nozzle to a high impedance state for a predetermined period. The pulse generator forms, from setting data respectively stored in an ejection both-side waveform setting register and a second high impedance setting register, an ejection both-side driving pulse for setting electrodes of ink chambers communicating with ejection both-side nozzles to the high impedance state for the predetermined period. The pulse generator outputs signals of the formed driving pulses to an inkjet head.