1. A periphery monitoring device comprising:a first storage that stores therein road surface information in a moving direction of a vehicle including a plurality of wheels, the road surface information being imaged by an imager of the vehicle;
a controller that generates underfloor information on an underfloor region of the vehicle from the road surface information stored in the first storage, the underfloor region being a road surface previously imaged by the imager and including at least part of a region of the wheels of the vehicle in a current position on the previously imaged road surface;
a second storage that is nonvolatile and stores therein, at the time of power-off of the vehicle, the underfloor information which is generated on the basis of a stop position of the vehicle; and
a display that displays the underfloor information stored in the second storage, upon power-on of the vehicle.