To provide a rotating machine capable of minimizing loss of compressor inner circulation and improving efficiency of driving power as preventing a seal from being destroyed.

A high pressure multistage centrifugal compressor (a rotating machine) 1, having a low pressure compressor (a low pressure rotating machine) 3, a high pressure compressor (a high pressure rotating machine) 4 and a drive unit 2 connected together in series is provided with a control valve 31 intervened in the midway of a pipeline of a seal line 11, a suction pressure detector 34 for detecting suction pressure of the high pressure compressor 4, and controller 37 for controlling the control valve 31 in accordance with a suction pressure signal 35 output by the suction pressure detector 34.