To provide a reliable centrifugal separator having a long life attained by preventing liquids present in its rotor chamber, such as condensation water and a sample liquid, from infiltrating the inside of its driving device through the vicinity of the rotary shaft, and thereby preventing problems, such as deterioration, corrosion, and defective insulation, of its bearing and motor.

The centrifugal separator includes a container constituting the rotor chamber for housing a rotor, the driving device disposed outside the container, and the rotary shaft 21 extending from the driving device into the rotor chamber penetrating the container and having the rotor attached to its tip. A penetrable member (5) that allows the rotary shaft 21 to penetrate is formed on the container. An elastic member 4 having an open end is attached to the rotary shaft 21 at the side of the rotor chamber. The open end 4b of the elastic member 4 is constituted to contact the penetrable member (5) when the rotor stands still, and to be distanced therefrom when the rotor rotates. A conical protrusion 5a protruding towards the rotor chamber is formed on the penetrable member (5), and the open end 4b of the elastic member 4 contacts the protrusion 5a.