Numerical model of evacuation behavior of people from the inundated underground space was investigated in this study. Information about a human behavior was taken into account as much as possible, a walking velocity, for example, was evaluated on the basis of relation between it and the congestion density of crowd. It was considered that the movement of each people was affected by both the movement by others and the approching flow of water on the floor. Numerical simulation was conducted in the relatively large scale model of underground space. It can be concluded that the present model works well and the reasonable simulation of evacuation behavior is possible to be realized.