A piezoelectric transformer type high-voltage power source apparatus to control an output voltage from a piezoelectric transformer to a load, and an image forming apparatus including the same, the piezoelectric transformer type high-voltage power source apparatus including: an output voltage detection unit to compare the output voltage with an output control voltage, and to output a digital value according to the comparison; and a driving control unit to control a driving frequency and a duty rate of the piezoelectric transformer according to the digital value. Accordingly, the piezoelectric transformer type high-voltage power source apparatus can stably perform frequency and duty rate control without experiencing an abnormal oscillation or uncontrollable state due to a manufacturing irregularity of particular components and/or a change in temperature, and a high voltage can be output within a short rise time.