PURPOSE: To provide an inexpensive water shielding sheet capable of surely preventing the intrusion of sewage into the soil with a simple structure and to furnish a water shielding device using the sheet.

CONSTITUTION: A water-permeable material 4 is interposed between a lower sheet 2 and an upper sheet 3 to constitute the water shielding sheet 5. The water-permeable material 4 is formed by laminating and integrating a water- permeable material consisting of a synthetic-resin nonwoven fabric on both sides of a core consisting of many ribs parallel to one another in the longitudinal direction and a substrate integrated with the rib and having a fish bone- shaped or wavy section and has the many water passages surrounded with the rib, water-permeable material and substrate. One end of the sheet 5 is sealed with a cap, and the other end is connected to a vacuum source through a connecter having many small holes.