A blood component collecting apparatus structured so that in each of the transition from the first plasma collecting step to the first constant-rate plasma circulating step and the transition from the second plasma collecting step to the second constant-rate plasma circulating step, the liquid feeding rate of second liquid feeding pump is increased while continuing the operation of first liquid feeding pump. Accordingly, in each of the first constant-rate plasma circulating step and the second constant-rate plasma circulating step, while collecting plasma in a plasma collection bag, not only is the plasma collected in the plasma collection bag circulated into a blood storage space of centrifugal separator via a plasma circulation line, etc. but also the flow rate of liquid component introduced in the blood storage space is made greater than that of liquid component introduced in the blood storage space during the plasma collecting step.
