To increase gas flow rate without varying the size as a whole by providing an outlet passage apart from a seat surface of a seat member, and forming an outlet opening in space between the outer circumference of this seat member and the inner circumference of a valve chest.

When gas to be controlled reaches an opening 41 by through an inlet passage 43 of a seat block 4, a laminated piezoelectric element is expanded or contracted by receiving a signal from a control circuit part, making a metallic diaphragm 51 abut to or separate from the seat member 42, and a clearance between the seat member 42 and the metallic diaphragm 51 is adjusted into a preset flow rate. Subsequently, the gas reaches an outlet opening 44 after passing through this clearance between the metallic diaphragm 51 and the seat member 42 from the opening 41, and it is discharged through an outlet passage 35. Since the outlet passage 35 is provided in a position apart from the seat member 42, when the gas flows into the outlet opening 44 from the opening 41, it flows through the clearance between the seat member 42 and the metallic diaphragm 51, so that abut 1.3 times of the normal gas volume can flow.