A head drive apparatus of an ink jet printer having: a plurality of nozzles for jetting liquid drops that are provided for an ink jet head; a plurality of actuators provided in correspondence to the nozzles; and a drive unit that applies a drive signal to the actuators, wherein the drive unit comprising: a drive waveform generator that generates a drive waveform signal being standard of a signal to control drive of the actuators; a modulator that modulates a pulse of a drive waveform signal generated by the drive waveform generator; a digital power amplifier for amplifying power of a modulated signal subjected to the pulse modulation by the modulator; and a low pass filter for smoothing 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.