PROBLEM TO BE SOLVED: To provide a tide prevention shutter for a building having a tide prevention function when fully shut, in which tide prevention slats 5 and 6 can be easily exchanged when being damaged by flooding and the like.SOLUTION: In a tide prevention shutter, a notch 2c is formed on an outdoor-side plate face part 2b of a guide rail 2, and a closing plate 2d for closing the notch 2c is arranged to protrude toward the outdoor side. Further, an expansion member 13 is detachably provided inside the closing plate 2d so as to press a shutter curtain 1 toward an indoor-side plate face part 2e side when the curtain is fully closed, for exerting a tide prevention function. When exchanging tide prevention slats 5 and 6, the tide prevention member 13 is removed to make an indoor side portion of the closing plate 2d be a wide space S, and by taking advantage of the wide space S, the tide prevention slats are made exchangeable.
