The piezoelectric actuator includes a piezoelectric element structure (100) which has at least one piezoelectric element (120), and a working edge (130) for directing driving force on a driven body (MB), wherein the working edge (130) oscillates in response to deformation of the piezoelectric element (120). The piezoelectric actuator further includes a driver circuit (300) for applying voltage to the piezoelectric element (120); and a drive control circuit (200) for inducing oscillation of the working edge (130) by supplying a drive signal (DV, #DV) of rectangular waveform to the driver circuit (300). The drive control circuit (200) is capable of reversing the drive direction of the driven body (MB) by changing the duty ratio of the drive signal (DV, #DV).