A flow rate ratio variable type fluid supply apparatus includes a flow rate control system supplying gas of flow rate Q that is diverted to first flow diverting pipe passage and second flow diverting pipe passage with prescribed flow rates Q1/Q0 so gas is supplied to a chamber, and a first orifice having opening area S1 is installed on the first flow diverting passage, and the second flow diverting passage is connected to a plurality of branch pipe passages connected in parallel, orifices having opening area installed on the branch passages, and open/close valves installed on all, or some of, the branch passages so gas is diverted to flow diverting passages with flow rate ratio Q1/Q0 equivalent to the ratio of the first orifice and the total opening area S2o of flow passable orifices of the second flow diverting passage by regulating total opening area of the flow passable orifices.