PURPOSE: To recover blood remaining in a leukocyte removing filter under aseptic condition by a system wherein an upper bag, the leukocyte removing filter and a lower bag are connected in this order with a communicating pipe in series in a closed system and a part for feeding air into a part between the upper bag and the leukocyte removing filter is provided on a pipe branched from the communicating pipe.

CONSTITUTION: A blood bag 1 and a separation bag 5 are made of polyvinyl chloride and blood and an anti-coagulant are stored in the blood bag 1. A line 2 is a tube and is branched between the blood bag 1 and a leukocyte removing filter 3 and a part 4 for feeding air is provided on the apex part of the branched tube. The blood in the blood bag 1 passes through the line 2 and flows into the leukocyte removing filter 3 to filter the blood and the blood which has passed through the leukocyte removing filter 3 is stored in the separation bag 5. When the blood bag 1 becomes empty, air in the part 4 is sent into the blood bag 1 and the leukocyte removing filter 3 by grasping the part 4 and the blood remaining in the filter is recovered in the separation bag 5.