A blood component separation device includes a centrifugal separator and a container for containing a predetermined blood component which is centrifugally separated and is configured to perform a plurality of steps of collecting a predetermined blood component which is separated. The blood component separation device includes a calculation unit which calculates an estimated extracorporeal circulation volume from a hematocrit value calculated by correcting a hematocrit value measured with a blood cell counter. The calculation unit calculates a correction value used in the correction from a data value of the estimated extracorporeal circulation volume of a plurality of immediately preceding collecting operations and a data value of sampled blood volume measured in the first cycle of each of the plurality of immediately preceding collecting operations.
