Abstract: A flow controller (1), comprising a valve body (4) having flow paths forming an inlet and an outlet of fluid, a diaphragm (6) held fixedly between the valve body and a bonnet (5), and an operating mechanism (7) moving the diaphragm vertically, wherein the valve body flow paths communicate with each other through a projection-free communication path (8), the a diaphragm is formed so that, when lowering, it comes into close contact with the communication path so that it closes the flow path and, when rising, the center part thereof is recessed so that an area near the outer peripheral part is raised, and a curved surface (52), to which the outer upper surface (63) of the raised part is closely fitted, is formed on a bonnet on the inner lower surface of a diaphragm holding part (51).

Abstract: A fluid controller (1), having a valve body (4) having flow paths used as inlet and outlet for a bonnet (5), and an operating mechanism (7) moving the diaphragm in vertical direction, wherein the flow paths of the valve body communicates with each other through a protrusion-free communication path (8), the diaphragm is fitted closely to the communication path when lowered so as to close the flow path and, when raised, the center part of the diaphragm is recessed and its part near the outer periphery part is protruded, and also a curved surface (52) to which the outer upper surface (63) of the protruded part is closely fitted is formed on the bonnet at the inner lower surface of a diaphragm holding part (51).