PURPOSE: To provide a drive circuit which can detect resonance state with a simple circuit configuration accurately.

CONSTITUTION: In a drive circuit of transformer drive type consisting of a rectifier 9, an A/D converter 10, a microcomputer 11, a variable frequency oscillator 2, a phase shifter 3, switching circuits 4 and 5 for generating pulses, drive electrodes 1a and 1b of a motor etc., the natural electrostatic capacity of an vibration wave motor and the inductance of the secondary winding of a transformer constitute a parallel LC circuit so that the LC parallel circuit also turns into an electrically resonated state when the vibrator of the motor turns into a mechanically resonated state, the circuit impedance is minimized, and hence the output voltage of the secondary winding of the transformer is extremely reduced. A voltage-divider circuit consisting of resistors R2 and R3 is connected in parallel to the secondary winding of a transformer 6 to detect that the vibrator (an excitation element 1 is shown) of the vibration wave motor turns into a resonated state.