To provide a bag which can efficiently filter soil of high water content deposited in a river, a lake, or the like, to a level where waste water treatment is unnecessary and which can be suitably used to confine the water-containing soil, and to provide a method for confining the water-containing soil by using the bag.

The bag is used for dehydrating the water-containing soil, the bag is made of a multifilament yarn textile of a synthetic fiber and a plurality of bags are mutually combined.