To provide a new water-absorbing medium and a method for concentrating a suspension using it.

The water-absorbing medium is a cross-linked polymer cross-linked with a layered clay mineral, includes a thermosensitive polymer gel having hydrophilicity/hydrophobicity reversibly changing at the phase transition point. In the method for concentrating the suspension, the water-absorbing medium and the suspension are brought into contact with each other in a temperature zone in which the thermosensitive polymer gel shows hydrophilicity, so that the suspension is concentrated.