PURPOSE: To recover a concentrated macromolecular solution in a maximal amount from a holding liquid storage device of this apparatus by subjecting the apparatus with a membrane supporting body having a filtrate duct for holding a semipermeable membrane together with a hermetic sealing member to centrifugal separation.

CONSTITUTION: The membrane supporting body 14 has a filtrate sleeve 22 for preventing the closure of air venting between a skirt 16 for fitting of a filtrate cup 18 and the filtrate cup 18 together with ribs 20 for discharge. The membrane supporting body 14 has the filtrate duct having a flat meshed surface allowing the passage of flow at a high velocity and three discontinuous arcs defining annular channel holes. The filtrate can be passed from the membrane to the filtrate cup 18 by these arcs. The filtrate cup 18 containing the filtrate is removed from the apparatus and the apparatus is turned over in such a manner that a holding liquid cup 2 comes to the underside of a sample storage device 6 in order to place the microconcentrator to a recovering mode. Next, the apparatus is subjected to the centrifugal separation in the turned over direction for a short time at a low speed, by which the maximal amount of the holding liquid is discharged into the holding liquid cup 2.