Flow ratio control device, program for flow ratio control device, and flow ratio control method

To provide a flow ratio control device with which it is possible, not only to achieve a target flow ratio, but also to control the time required to achieve the target flow ratio, provided is a flow ratio control device, comprising: a main flow path; a plurality of branch flow paths which branch from a terminal end of the main flow path; a plurality of fluid control devices which are disposed upon each of the branch flow paths, and each of which comprises a valve and a pressure-type flow sensor which is positioned to the downstream side of the valve; and an operation setting unit which, on the basis of a target flow ratio, sets one of the fluid control devices from among the plurality of fluid control devices to operate in a flow speed control mode for controlling a flow speed of a fluid to the upstream side of each of the valves, and sets the other fluid control devices to operate in a flow rate control mode for controlling the flow rate on the basis of a target flow rate.