Blood line belongs to blood purification appliances. A blood line assembly which is capable of being handled relatively easily includes a first tube, a second tube having a second tube body and two branch tubes branching from the second tube body, and a connector having plugs on which the first and branch tubes are removably fit. In the blood line assembly, by removing the first tube and the branch tubes from the connector, the first tube and the branch tubes can be connected to respective catheters positioned in a patient.