A piezoelectric actuator has a piezoelectric element adapted to simultaneously generate first and second vibration modes in response to a voltage applied thereto. The piezoelectric element has one outer surface including a first region and a second region projecting from the first region, while the second region comes into contact with a body to be driven, so as to cause a frictional force with the body to be driven. Without restricting the size of the piezoelectric element, the piezoelectric actuator inhibits its driving state from fluctuating.