To provide a water cutoff device capable of being stored compactly without causing a traffic obstruction in normal time and cutting off water easily and surely when in use.

A water cutoff device 1 for cutting off water at a building entrance comprises: a rubber bag-like body 70 which is arranged to cross the entrance and rises from the fallen position to seal off the entrance by introducing gas therein through a communicating hole; a horizontal plate 20 which is arranged to horizontally cover the bag-like body 70 in the fallen position; and a pair of vertical plates 30 and 40 which are arranged almost vertically on both sides of crossing direction of the entrance to the horizontal plate 20 to cover the bag-like body 70. The horizontal plate 20 is configured to be raised in contact with the surface of bag-like body 70 due to rising of the bag-like body 70, and intermediate plates 50 and 60 are openably and closably provided between the horizontal plate 20 and the pair of the vertical plates 30 and 40 respectively.