To provide a simple, inexpensive and closed cell collection system having a means for reserving hematopoietic stem cells, etc., short in handling time, capable of easily obtaining concentrated hematopoietic stem cell fractions from a stock cell suspension, thus useful for, e.g. therapy of leukemia, etc.

This cell collection system consists of a closed circuit constituted by connecting in series at least a means 1 to reserve a collected stock cell suspension, a 1st catch means 2 to catch leukocytes but pass erythrocytes, and a means 4 to reserve an erythrocyte-contg. fluid running out of the catch means 2, in this order, and also has a 2nd catch means 3 situated before the inlet of the 1st catch means 2 and after the means 1, or situated on the upstream side of the means 4 and branched off the outlet of the 1st catch means 2 to catch granulocytes and monocytes but pass hematopoietic stem cells and a means 5 to reserve the hematopoietic stem cells running out of the catch means 3. It is preferable that there is provided a rinse means to feed a relevant fluid via the 1st catch means 2 to an erythrocyte recovering means.