Abstract: A screw press dehydrator provided with a cake cutter which is formed of a plurality of stationary plates and sliding plates each containing circular holes and disposed alternately around a screw barrel at a position closer to the discharge outlet side thereof, with a screw laid through the circular holes. A smaller circular hole is provided in each of the sliding plates. A revolutionary motion is imparted to the sliding plates such that the centers of the circular holes in the sliding plates may describe a circle of a fixed radius about the centers of the circular holes in the stationary plates and the circumferences of the circular holes in the revolving sliding plates may remain in contact with the circular holes in the stationary plates.