PURPOSE: To avoid the leak of a sample from the sealed part of a continuous rotor by a method in which the injection of a sample is interrupted by a controlling means when a centrifugal machine is transferred to decelerating operation or the supply of power is interrupted.

CONSTITUTION: A sample interruption means 9 is provided to the way of a pipeline 4 through which a separating sample is injected to the germ free type continuous rotor of a centrifugal machine 2. When the supply of power is interrupted or the centrifugal machine 2 is transferred to decelerating operation, the injection of sample is stopped by operating the sample interruption means 9 by the signal of a controlling means 10. Thus, the leak of sealant liquid or a sample from the continuous rotor can be eliminated and therefore, a safe and germ free separating operation can be attained.