A piezoelectric actuator includes a suspension plate, a piezoelectric ceramic plate, an outer frame and a bracket. The suspension plate is permitted to undergo a curvy vibration from a middle portion to a periphery portion. The piezoelectric ceramic plate is attached on the suspension plate. When a voltage is applied to the piezoelectric ceramic plate, the suspension plate is driven to undergo the curvy vibration. The outer frame is arranged around the suspension plate. The bracket is connected between the suspension plate and the outer frame for elastically supporting the suspension plate, and includes an intermediate part formed in a vacant space between the suspension plate and the outer frame and in parallel with the outer frame and the suspension plate, a first connecting part arranged between the intermediate part and the suspension plate, and a second connecting part arranged between the intermediate part and the outer frame.