To provide a drying treatment system or the like which enhances the evaporation efficiency of moisture comprised in organic sludge and the drying speed of the organic sludge, downsizes the treatment equipment of the organic sludge, and further can efficiently treat condensed water.

The drying treatment system 1 for organic sludge comprises: an organic sludge drying apparatus 6 with a heat source for drying organic sludge SL as an exhaust gas G1 of ≤450°C exhausted from cement production equipment 2; a water vapor condensing apparatus 8 condensing water vapor generated by drying by the organic sludge drying apparatus 6; and an incineration ash water-washing apparatus 10 utilizing water W condensed by the water vapor condensing apparatus 8 for the water washing of incineration ash A. The system is preferably provided with a decomposition substance adding apparatus 7 adding a substance decomposing protein in the organic sludge SL at the inside of the organic sludge drying apparatus 6 or at the prestage thereof.