To prevent the conversion of sludge to clay and the occurrence of clogging without imposing a burden on an operator by automatically stopping sludge charge into a dryer for a while when the amount of charge exceeds the drying capacity and by automatically restarting the sludge charge when the load decreases sufficiently to dry sludge.

In the drying apparatus for water-containing sludge, water- containing sludge is sent from a water-containing-sludge hopper by a screw conveyor into an upwardly pointed dryer; sludge discharged from the upper part of the upwardly pointed dryer is introduced into the upper part of a vertical dryer, and sludge discharged from the lower part of the vertical dryer is introduced into a horizontal dryer. When the load current of the motor of the vertical dryer exceeds an overload-detecting current value, the operation of the former process of the vertical dryer is stopped to automatically stop the sludge charge into the vertical dryer for a while. When the load current of the motor lowers to the reset current value, the operation of apparatus of the former process is restarted to automatically restart the sludge charge into the vertical dryer. Thus, the amount of charged sludge is controlled.