A pressure control device includes a pressure control valve, a flow resistance provided downstream of the pressure control valve, a first pressure sensor for measuring a gas pressure between the pressure control valve and the flow resistance, a second pressure sensor for measuring a gas pressure downstream of the flow resistance, and a calculation control circuit connected to the first pressure sensor and the second pressure sensor, wherein the pressure control device controls the gas pressure downstream of the flow resistance by adjusting an opening degree of the pressure control valve based on an output of the second pressure sensor regardless of an output of the first pressure sensor control, and calculates the flow rate of the gas downstream of the flow resistance, based on the outputs of the first and the second pressure sensors.