To provide a centrifugal separator which can reduce the adverse effect of windage loss during rotor rotation and thereby, save energy.

This centrifugal separator 1 includes (1) a rotor 12 rotating inside a rotor chamber 11 which stores a sample, (2) a door 9 which opens/closes the rotor chamber 11, (3) a drive device 4 for rotatably driving the rotor 12, and (4) a control device 5 for controlling the actuation of the drive device 4. In addition, an inner lid 15 whose outside diameter is smaller than the inside diameter of the rotor chamber 11, is arranged in an ascending/descending manner, inside the rotor chamber 11. Further, the volume of a rotation space 11a, for the rotor 12, which is compartmentalized by the inner lid 15. is diminished by making the inner lid 15 descend at least, during operation. Besides, an ascending/descending means 16 for ascending/descending the inner lid 15 is fitted to the door 9, so that the door 9 can open/close when the inner lid 15 is located in the upper limit home position.