To easily shield a strainer attached to both end parts of a 'T'-shaped water-intake pipe.

This shielding device is composed of the first cylindrical part 2 opened in its both ends, and the second cylindrical part 3 of which the both ends are closed by bottom parts 32. The second cylindrical part 3 is connected to a tip part of the first cylindrical part 2 in its central part. Water-tight fasteners 5, 5 are provided in a cross part crosses with a plane (not shwn in Figure) including respective axial lines of the first and second cylindrical parts 2, 3 and a circumferential wall of the first cylindrical part 2. The fasteners 5, 5 are laid ranged over from the base end to the tip of the first cylindrical part 2 and extended further along an axial line of the second cylyidrical part 3 upto its end part side. The fasteners 5, 5 are opened to divide the first cylindrical part 2 into semi-cylindrical parts 2A, 2B, and to open also the central part of the second cylyidrical part 3 widely.