A piezoelectric actuator 60 includes a piezoelectric element 10 expanding and contracting according to a state of an electric field, a pedestal 20, a vibration film 30, and a support member. In the vibration mode of the divided vibration occurring in the piezoelectric actuator in a high frequency band, one or more reinforcement members 50 are selectively disposed on an upper surface or a lower surface of the piezoelectric element 10, in a region where a node of divided vibration occurs. With such configurations, the vibration mode can be changed in the piezoelectric element 10. Therefore, in the frequency sound pressure level characteristics, the divided vibration causing hills or valleys (peaks or dips) can be effectively suppressed, thus enabling the achievement of flatness of frequency sound pressure level characteristics and of reproduction of excellent sound.