The present invention provides a zonal centrifuge which has superior workability and functionality when a sample is filled and extracted. An oil bearing fitted to an outer circumference of a lower tube of a rotor is arranged on an internal face of a bearing housing fixed over a door adapter of the centrifuge. As the oil bearing and the lower tube are lubricated, a vacuum environment in a rotor rotating chamber is maintained. A rotating seal located at an upper leading end of the lower tube of the rotor and a fixing seal facing the rotating seal are arranged and provided in a sealed space formed by a mechanical seal member and the bearing housing, and the fixing seal is so manipulated as to be able to freely join and separate from the rotating seal.