A fluid regulator including, in a housing, a nozzle flapper mechanism, a diaphragm displaceable by the nozzle back pressure of the nozzle flapper mechanism, a valve body for controlling fluid communication through a fluid passage in accordance with displacement of the diaphragm, and a sensor for picking up a change in output fluid pressure from the fluid passage as a change in an electric signal. The nozzle flapper mechanism includes an electrostrictive element positioned closely to the nozzle of the nozzle flapper mechanism. Displacement of the electrostrictive element with respect to the nozzle is controlled by a differential signal resulting from comparison between an electric input signal and an electric signal from the sensor. The nozzle back pressure is varied dependent on the displacement of the electrostrictive element for thereby displacing a valve body in the fluid passage until the valve body is brought into equilibrium.