Abstract: A dehydration treatment apparatus for sludge wherein organic sludge and a modifying/setting agent are charged into a rotating drum and the sludge is dehydrated and dried. The apparatus comprises a rotating drum, a sludge charging hopper arranged on the inlet side of said rotating drum, a discharging screw arranged on the outlet side of the rotating drum, at least two rectangular blades that are projected from each of circular surfaces arranged toward the feeding direction from the inlet side of the inner circumferential surface of the rotating drum and are slanted downward at a prescribed angle toward the feeding direction, and an agitating/feeding means wherein the positions of the blades on the circular surfaces are made different stepwise successively in the direction of rotation toward the feeding direction so that sludge may be scraped up by the blades on the fore circular surface to be fed forward.