A flow control device comprising: a housing; a diaphragm splitting the housing into a gas chamber side to which gas is introduced and a fluid chamber side through which fluid passes, and being activated by differential pressure between the gas chamber side and the fluid chamber side; and a valve body which operates in integration with the diaphragm to regulate flow of the fluid introduced into the fluid chamber side, wherein the diaphragm includes: a base part provided in a substantially central part of the diaphragm; a thin film part provided on an outer peripheral edge of the base part, the thin film part being thinner than the base part; and an outer peripheral edge part provided on an outer peripheral edge of the_thin film part, the outer peripheral edge part being thicker than the thin film part, wherein an opposing surface which is provided on the fluid chamber side and opposite to the diaphragm includes a retaining form which retains a shape of the thin film part deformed by the differential pressure, a gas chamber side surface of the thin film part is covered by a permeation protection sheet for preventing gas permeation from the gas chamber side to the fluid chamber side, an outer peripheral edge of the permeation protection sheet is pushed to the outer peripheral edge part by a first annular projection, and an inner peripheral edge of the permeation protection sheet is pushed to the base part by a second annular projection. a housing; a diaphragm splitting the housing into a gas chamber side to which gas is introduced and a fluid chamber side through which fluid passes, and being activated by differential pressure between the gas chamber side and the fluid chamber side; and a valve body which operates in integration with the diaphragm to regulate flow of the fluid introduced into the fluid chamber side, wherein the diaphragm includes: a base part provided in a substantially central part of the diaphragm; a thin film part provided on an outer peripheral edge of the base part, the thin film part being thinner than the base part; and an outer peripheral edge part provided on an outer peripheral edge of the_thin film part, the outer peripheral edge part being thicker than the thin film part, wherein an opposing surface which is provided on the fluid chamber side and opposite to the diaphragm includes a retaining form which retains a shape of the thin film part deformed by the differential pressure, a gas chamber side surface of the thin film part is covered by a permeation protection sheet for preventing gas permeation from the gas chamber side to the fluid chamber side, an outer peripheral edge of the permeation protection sheet is pushed to the outer peripheral edge part by a first annular projection, and an inner peripheral edge of the permeation protection sheet is pushed to the base part by a second annular projection. a base part provided in a substantially central part of the diaphragm; a thin film part provided on an outer peripheral edge of the base part, the thin film part being thinner than the base part; and an outer peripheral edge part provided on an outer peripheral edge of the_thin film part, the outer peripheral edge part being thicker than the thin film part, wherein an opposing surface which is provided on the fluid chamber side and opposite to the diaphragm includes a retaining form which retains a shape of the thin film part deformed by the differential pressure, a gas chamber side surface of the thin film part is covered by a permeation protection sheet for preventing gas permeation from the gas chamber side to the fluid chamber side, an outer peripheral edge of the permeation protection sheet is pushed to the outer peripheral edge part by a first annular projection, and an inner peripheral edge of the permeation protection sheet is pushed to the base part by a second annular projection.