Gas supply facility of a chamber and a method for an internal pressure control of the chamber for which the facility is employed

The present invention prevents substantial reduction of flow rate control accuracy in a small flow quantity range, achieves accurate flow rate control over the entire range of flow rate control, and also allows control of a wide pressure range of a chamber with accurate flow rate control. Specifically, a gas supply facility having a plurality of pressure type flow controllers connected in parallel, and a third controller to control operation of the pressure type flow controllers to supply a desired gas exhausted by a vacuum pump to a chamber while controlling its flow rate, is provided wherein one pressure type flow controller is a controller used to control a gas flow rate range up to 10% of the maximum flow rate supplied to the chamber, while the remaining pressure type flow controllers are made to be ones controlling the rest of the gas flow rate range.