An actuator includes a first electrode disposed on the top surface of a ceramic substrate (for example, zirconium oxide), a piezoelectric/electrostrictive substance disposed on the first electrode, and a second electrode disposed on the piezoelectric/electrostrictive substance, wherein the input of an electric power alters the volume of the piezoelectric/electrostrictive substance. The piezoelectric/electrostrictive substance contains a plurality of crystal grains that have a wavy structure composed of wavy grain boundaries including concave portions and convex portions. The crystal grains contain ABO3 as the main component. The A site is Pb, and the B site contains such an amount of M that M becomes excessive after the piezoelectric/electrostrictive substance is formed (wherein M is at least one element selected from Mg, Ni, and Zn). The crystal grains of the piezoelectric/electrostrictive substance are oriented in the electric field direction, independently of the orientation of the substrate.