A high-voltage power-supply apparatus comprises a controller configured to output a control signal containing a pulse with a variable drive frequency; a switching unit configured to be switched by the control signal and output a drive signal; a piezoelectric transducer having a predetermined resonant frequency, and configured to be driven by the drive signal and output a high-voltage output voltage; a current detector configured to detect an electric current of a load connected to an output side of the piezoelectric transducer and output a current-detection result; and a lower-limit-value setup unit configured to set a frequency lower limit value for the drive frequency of the controller. The controller is configured to vary the frequency lower limit value in accordance with the current-detection result.