A blood bag system (10) includes a blood bag (14) to which centrifugal force is provided in a state where whole blood or a blood component is stored, and a first tube (22) that circulates a fluid centrifugally separated from the blood bag (14). The first tube (22) includes an extending portion (112) extending in an approximately perpendicular direction to a centrifugal direction into which the centrifugal force is applied. Further, a branch tube (114) that can store blood existing in the extending portion (112) is provided at a side of the centrifugal direction of the extending portion (112).
