The blood bag system includes: a blood treating filter for treating a blood a first bag for containing therein a blood to be supplied to the blood treating filter a second bag for containing therein the blood treated by the blood treating filter storage solution supply which supplies a blood component storage solution to the blood treating filter a third bag into which a blood remaining in the blood treating filter replaced by the blood component storage solution is transferred and in which the recovered blood is temporarily contained and a fourth bag to which a blood component separated from the treated blood contained in the second bag is transferred and in which the transferred blood component is contained.
