Abstract: A pressure-swing adsorption type gas separator system includes two adsorption vessels and a switching valve for placing each of the adsorption vessels alternately in communication with a raw gas source and an exhaust gas line so that a pressurized adsorption process and a reduced-pressure desorption process are sequentially carried out in each of the vessels. The switching valve is a four-port rotary valve having four ports connected to the adsorption vessels, a raw gas source and an exhaust gas line and is driven by a rotary drive. Preferably, the rotary drive is a drive motor for a pressurizing pump provided in a raw gas line, and the four-port rotary valve is connected to the drive motor via a speed reducer.