A piezoelectric actuator includes a vibrating body including a piezoelectric device; a driving circuit that supplies a driving signal to the piezoelectric device; a phase difference detecting circuit that detects a phase difference between the driving signal and a detection signal detected based on vibration of the vibrating body; and a frequency controller that controls the frequency and power of the driving signal, wherein the frequency controller sets the power to an upper limit voltage value when the frequency is changed so that the phase difference falls within a predetermined range and sets the voltage to a lower limit voltage value smaller than the upper limit voltage value when the phase difference is outside the predetermined range.