To provide a building with an anti-tsunami shelter capable of being used as a private room integrated with a roof of the building at normal times and as a shelter for evacuation which is naturally separated from the building and floats by a force of water when the roof of the building is submerged by tsunami or flood.

A roof section of a building A is formed of a shelter B having a sealed space L, the shelter B being disposed above a living section C. The shelter B preferably consists of at least a sealable shelter body 1 having an upper part formed in a roof shape and a lower part formed nearly in a ship bottom shape, an opening/closing door 11 and a ventilation window 12 mounted to the shelter body 1, and a storage shelf 3 mounted inside the shelter body 1. Moreover, the living section C and the shelter B are preferably fixed and integrated together via mounting means 2.