To provide a drive unit for ultrasonic motor which detects a resonance frequency of a piezoelectric element without using a sensor, etc., and can drive an ultrasonic motor efficiently.

When an ultrasonic motor 26 is started up, a variable oscillator controlling circuit 12 and a variable oscillator 13 supply a frequency sweep signal between an electrodes 26a and an electrode 26b or between the electrode 26a and an electrode 26c. At that point, a detection circuit 17 monitors the output voltage of the electrode which is not supplied with the sweep signal and a comparing circuit 22 compares the voltage with a reference level and then stops the sweeping of a frequency by the variable oscillator controlling circuit according to the comparison result. After that, the ultrasonic motor is driven at a constant frequency.