PURPOSE: To discharge materials to be dehydrated without hoisting or tilting a dehydrating tank by constituting the dehydrating tank of rotary type in such a way that the bottom plate thereof is made free to open.

CONSTITUTION: Materials to be dehydrated are charged from a conveyor 34 into the dehydrating tank 4 of a dehydrator 1 while a bottom plate 12 is held closed. When the prescribed height is attained, the tank 4 is rotated and the materials are dehydrated by centrifugal forces. Upon completion of the dehydration, the tank 4 is rotated at a low speed, and a solenoid 31 is operated to project an ejecting bar 30 inward. The bar 30 is brought into abutment on the bottom end part of a hook 26 pivotted to the outer side of the tank 4 to disengage the engaging piece 27 of the plate 12 from the engaging grrove 26' of the hook 26, whereby the plate 12 is released and the materials are dropped downward and are thereby discharged. In this time, a ring 23 is kept pulled upward to prevent the contact of the abutting piece 15 of a lever 14 with the turning bottom plate 12. Upon completion of the discharging of the materials, the ring 23 is moved downward by the revolution of a geared motor 16 to force the piece 15 downward, thereby moving the plate 12 in a closing direction.