Abstract

A valve body which is driven by a valve body-driving portion constructed from a piezoelectric stack to open and close a valve mouth. The piezoelectric stack consists of piezoelectric disc elements having a thickness of 0.1 to 0.5 mm and a diameter of 10 to 50 mm, whose upper surface and lower surface are both plated, and thin metallic plates each having a thickness of 0.05 to 0.2 mm and being high in electric conductance, are alternately laminated one between the piezoelectric elements by one (the number of piezoelectric elements laminated is 100 to 200). Every other one of the thin metallic plates are connected to a positive polar lead and the remaining plates are connected to a negative polar lead, and a voltage-applying lead wire is connected with each of the lead wires. A driving force transmission member can be provided between the valve body-driving portion and the valve body for amplifying the amount of distortion of the piezoelectric stack to thereby allow adjustment of the amount of movement of the valve body and adapt the structure for handling large volumes of fluid.