To provide a dehydration apparatus for dehydrating matter to be treated such as muddy water or the like stably and properly over a long period of time without specially maintain the matter to be treated, and a treatment method using the same.

The dehydration apparatus 1 for a raw liquid Mb is constituted so as to dehydrate the raw liquid Mb containing flocculated floc formed from the matter Ma to be treated such as muddy water or the like and equipped with a box body 10 of which the top surface part 10a is set as the storage surface part 10b of the raw liquid Mb and a vacuum pump 11 for bringing the interior of the box body 10 to a predetermined vacuum atmosphere. The top surface part 10a of the box body 10 is constituted of a porous ceramic board body 10e.