Absorption liquid recirculating pipes fitted with absorption tower (absorber) recirculating pumps corresponding to individual spray headers are inserted from the void tower portion inside absorption tower, near the liquid surface of liquid trapping portion (recirculation tank), in the interior of the absorption tower, erected vertically from substantially the center of the absorption tower and connected to respective spray headers provided in multiple stages along the direction of gas flow. Multiple nozzles of each of the spray headers are disposed mutually concentrically or rectangularly on a plane orthogonal to the direction of flue gas flow within the absorption tower. Thus, there can be provided a wet flue gas desulfurization apparatus (system) that is capable of large-capacity flue gas treatment and that in a plant where highly efficient desulfurization of flue gas of high SOx concentration is demanded, even when the amount of liquid circulated through the absorption tower is increased, can avoid increasing of the height of absorption tower and the power of absorption tower recirculating pumps and can realize easily disposing of footpath for maintenance.