A fluid supply apparatus with a plurality of flow lines branching out from one pressure regulator with the flow lines arranged in parallel and constructed so that opening or closing one flow passage will have no transient effect on the steady flow of the other flow passages. Each flow passage is provided with a time delay-type mass flow controller MFC so that when one closed fluid passage is opened, the mass flow controller on that flow passage reaches a set flow rate Qs in a specific delay time &Dgr;t from the starting point. The invention includes a method and an apparatus in which a plurality of gas types can be controlled in flow rate with high precision by one pressure-type flow control system.