An advanced pressure type flow control device capable of accurately controlling a flow by using an experimental flow expression established to accurately fit to the actual flow of compressible fluid in a non-critical area, wherein the experimental flow expression of the compressible fluid in the non-critical area non-sound velocity area is expressed as Qc = KP2m P1 - P2n, and the fluid flow passing through an orifice 4 is calculated by using the expression Qc = KP2m P1 - P2n K is a proportional constant, m and n are constants so that the flow can be accurately and rapidly controlled to a specified one, and a pressure ratio P2/P1 = r provided by an upstream side pressure P1 and a downstream side pressure P2 is always compared with a critical value rc and the flow is calculated by using an expression Qc = KP1 under the critical condition of r rc so that the flow can be accurately and rapidly controlled to the specified one in correspondence to all conditions of the fluid.