In a method for manufacturing a piezoelectric actuator, a ceramic sintered body is prepared and a size of the ceramic sintered body is adjusted in a thickness direction defined below by grinding piezoelectric ceramic layers, included in the ceramic sintered body, located outermost in the thickness direction. In the ceramic sintered body, internal electrodes are each disposed between piezoelectric ceramic layers. The thickness direction is defined as the direction along the thickness of the piezoelectric ceramic layer. Each of the inert sections are disposed on at least one side of the active section, for driving the piezoelectric actuator, in the thickness direction. Dummy internal electrodes are arranged in the inert sections such that each of the dummy internal electrodes are each located between ceramic layers. The thickness of the piezoelectric ceramic layers disposed between the dummy internal electrodes increases with distance from the active section.