PURPOSE: To provide a tide prevention device having a water stop section, allowing easy handling and not requiring much space for storage and the preparation of storage space specifically.

CONSTITUTION: Pillars 2 and a base beam 3 having approximately U-shaped structure are provided on the exterior surface of the doorway or the like of a building enclosed with building walls 51. In addition, if a danger such as a high tide and a flood should occur, a cut-off screen 1 normally folded and stored in the beam 31 is lifted along the pillars 2 and extended on the operation of a mechanism within pillar members 21, thereby forming a tide prevention device.