To provide a structure and a method for installing a rat-proof member, which can facilitate work for installing the rat-proof member.

A building 10 is a unit type building in which a plurality of building units 20 are connected together. A floor girder 23 of the building unit 20 is provided along a foundation 11, on the foundation 11. A ventilation gap 16 is formed between the foundation 11 and the floor girder 23. A rat-proof member 40 is provided so as to close the ventilation gap 16. The rat-proof member 40 is fixed to the floor girder 23, and provided in the state of being pressed against an upper face 13 of the foundation 11 and elastically bending-deformed to an outdoor side.