In a small scaled plant intended for flexible manufacturing, a pure water supply system is provided at a low cost without reducing a production efficiency. A pure water system produces a plurality of grades of pure water which are supplied through pipes connected to points of use for cleaning, CMP, lithography, and the like. Upon receipt of a request signal from each point of use for starting to use a certain grade of pure water, a controller determines whether or not a required amount exceeds the capacity of the grade of pure water which can be supplied by the pure water system. If not, the controller sends a use permission signal to the point of use for permitting the same to use the pure water. When a certain use point is using the requested grade of pure water, the controller may not permit the requesting point of use to use the pure water until a use end signal is sent from the use point which is using the pure water.