Abstract: A hydroextractor in which a liquid material to be processed can be introduced into a hydroextracting chamber under a small pressure and the chamber can be filled with the material in a short period of time to thereby improve the operational efficiency, and a cake of the hydroextracted material can be easily removed from the hydroextracting chamber. For these purposes, this hydroextractor is arranged such that upper and lower filter cloths are provided at the top and the bottom of the hydroextracting chamber extending substantially horizontally, and that a diaphragm (8) shaped like an inverted dish is disposed on the upper surface of the upper filter cloth. Further, a pressure chamber is provided on the upper side of the diaphragm. The hydroextracting operation is performed by filling the liquid material in the hydroextracting chamber and generating a pressure in the pressure chamber so as to press the diaphragm downwardly.