PURPOSE: To improve an yield or a removal rate of blood components by accomplishing a separation and a recovery of the blood components quickly.

CONSTITUTION: This blood component separator 1 is provided with a first centrifugal separator 2 to separate blood into a plural blood components, a second centrifugal separator 3 to further finely separate the blood components into a plurality of blood components, a first line (blood introduction line) 4 to introduction the blood to the first centrifugal separator 2, a forth line (blood removing/returning line) 10 and a second line (blood component transfer line) 5 to transfer the blood components to the second centrifugal separator 3 from the first centrifugal separator 2. Then, a third line (blood component recovery line) 6 is arranged to recover the blood components obtained with the second centrifugal separator 3. Further pumps 71-73, a valve 8 to open or close the passage of the second line 5, a control means to control them and sensors 81-83 are arranged.