A method for manufacturing a piezoelectric actuator is provided. The method includes: forming a diffusion-preventive layer having an electrical conductivity on a partial surface thereof on a surface of a vibration plate formed of a metallic material; forming a piezoelectric layer on the surfaces of the diffusion-preventive layer and the vibration plate; forming an electrode in an area of the piezoelectric layer which overlaps the partial surface of the diffusion-preventive layer having the electrical conductivity; forming an extraction electrode in an area of the piezoelectric layer which does not overlap the diffusion-preventive layer; and heating the piezoelectric layer and the vibration plate after the piezoelectric layer is formed so as to diffuse metallic atoms of the metallic material of which the vibration plate is formed to the piezoelectric layer, thereby making the extraction electrode be in conduction with the partial surface of the diffusion-preventive layer having the electrical conductivity.