A countercurrent liquid-solid contacting apparatus having combined filtering and regenerating columns stacked one above the other. The filtering column has a liquid inlet and outlet, a liquid medium to be filtered being supplied into the filtering column through the liquid inlet and discharged to the outside through the liquid outlet after having passed upwardly through a bed of filtering material within the filtering column. The regenerating column has its bottom end opening into the filtering column and supplies a filtering material in an amount necessary to compensate for a reduction in the amount of the filtering material within the filtering column each time a portion of the filtering material in a lower region of the filtering column is withdrawn and then transported back into the regenerating column. Since the regenerating column is a closed vessel, pipe lines sealed to the atmosphere by liquid medium extending outwardly from the liquid outlet and also from the regenerating column have a predetermined relationship with each other.