A nozzle flapper mechanism includes an electrostrictive device, a plate member coupled to the electrostrictive device, a nozzle having an orifice facing the electrostrictive device or the plate member, and a controller for applying a voltage to the electrostrictive device to keep a nozzle back pressure constant or vary the nozzle back pressure. The electrostrictive device comprises a shim, piezoelectric ceramics members disposed on the shim, and thin-film electrodes disposed on the piezoelectric ceramics members, the electrodes having an area smaller than that of the piezoelectric ceramics members, the piezoelectric ceramics members having one end directly fixed in position on a stationary member.