An object of the present invention is to provide a fluid mixing system able to mix the fluids of different lines by any ratio and control the flow rates of even pulsating fluids, able to control the flow rate of even a pulsating fluid, compact in configuration and able to be installed in a narrow space, and enabling easy pipe laying and pipe connection at the time of installation.
In the system of the present invention, the feed lines 1, 2 are provided with fluid control valves 4, 10 controlling pressures of fluids by pressure operations of control fluids, flow rate measuring devices 3, 9 measuring actual flow rates of the fluids, converting the measured values of the actual flow rates to electrical signals, and outputting the same, and control units 5, 11 outputting command signals for controlling the opening areas of the fluid control valves to the fluid control valves or equipment operating the fluid control valves based on the errors between the measured values of the actual flow rates and flow rate settings. In the system of the present invention, for example, to obtain a washing solution for semiconductor production, hydrofluoric acid or hydrochloric acid is mixed with pure water by a ratio of 1 part to 10 to 200 parts.