Flow control valve and mass flow controller using the same

A flow control valve comprising

• a valve seat,
• a valve body which carries out an opening and closing action in a direction perpendicular to a contact surface of said valve seat,
• an elastic means which gives said valve body elastic force in a direction away from said contact surface or a direction approaching to said contact surface, and
• a driving means which drives said valve body in a direction opposite to the elastic force by said elastic means, wherein:
• said valve seat comprises an outer cylindrical member which has a discharge passage of fluid consisting of one or more holes for bringing an inner circumference side and an outer circumference side of said outer cylindrical member in communication with each other and a groove part formed on said outer circumference side in communication with said hole, and an inner cylindrical member which is disposed on the inner circumference side of said outer cylindrical member, has an inflow passage of the fluid on an inner circumference side of said inner cylindrical member, and has said contact surface on an upper end part of said inner cylindrical member, and
• a lower part of said outer cylindrical member and a lower part of said inner cylindrical member are airtightly fitted with each other.