Provided is apparatus for controlling flow rate of gases used in semiconductor device by differential pressure by generating differential pressure in a fluid path. A differential pressure generation element generates pressure difference in the fluid path of gases used in semiconductor device fabrication, a pressure, sensor which is installed at a bypass of the fluid path detects the pressure difference, and a central processing unit (CPU) measures and controls a flow rate of the gases, thereby the present invention is capable of controlling the flow rate precisely and rapidly, and enhancing the degree of purity of the gases by the filtering function of the differential pressure generation element itself.