A head drive apparatus of an inkjet printer includes nozzles and corresponding actuators that eject liquid drops. A drive unit applies a drive signal to the actuators. The drive unit includes a drive waveform generator that generates a drive waveform signal as a reference of a signal to control drive of the actuators. A modulator pulse modulates a drive waveform signal generated by the drive waveform generator. A digital power amplifier amplifies power of a modulated signal subjected to the pulse modulation. A low pass filter smoothes an amplified digital signal subjected to the power amplification by the digital power amplifier and supplying the signal as a drive signal to the actuators. An inverse filter provided in a subsequent stage of the drive waveform generator corrects at least the frequency characteristics of the filter to predetermined frequency characteristics, independently of the number of the actuators to drive.