A method of manufacturing a piezoelectric actuator, includes: forming a constraint force buffering layer, the constraint force buffering layer being made of a hardness control material of which hardness changes in accordance with temperature condition; raising the hardness of the constraint force buffering layer by cooling the constraint force buffering layer; and forming a piezoelectric element by a deposition method, on the constraint force buffering layer of which hardness has been raised, wherein: the hardness control material is a shape memory polymer, a glass transition temperature of the shape memory polymer is lower than an operating temperature occurring during driving of the piezoelectric actuator, and the constraint force buffering layer has a higher hardness at a temperature occurring during formation of the piezoelectric element which is lower than the operating temperature.