Disclosed is a gas processing apparatus which can be operated independently of the feed flow rate of a process gas. The gas processing apparatus comprises a compressor (1), a first processing unit (2) at the downstream side of the compressor (1), an expander (3) at the downstream side of the first processing unit (2), a second processing unit (4) at the downstream side of the expander (3), and a driver for driving the compressor (1), wherein the apparatus comprises a first pressure gauge (10) at the inlet of the compressor (1), a second pressure gauge (11) at the outlet of the second processing unit (4), a recirculation channel (24) between the outlet of the second processing unit (4) and the inlet of the compressor (1), a first pressure control valve (12) in the recirculation channel (24), a second pressure control valve (13) at the downstream side of the second pressure gauge (11), a tachometer (14) for measuring the rotation rate of the driver, and a controller for controlling at least one of the following in accordance with the measured pressure and rotation rate: the rotation rate of the driver, the first pressure control valve (12), or the second pressure control valve (13).