A flood detection device includes a detection result acquisition section, a weather information acquisition section and an identification section. The detection result acquisition section acquires a detection result that, on the basis of a plurality of kinds of running state data relating to running of a vehicle, detects flooding of a road on which the vehicle is running. The weather information acquisition section acquires weather information including at least one of rainfall information representing a measured rainfall amount in a region in which the vehicle is running or rainfall estimation information representing an estimated rainfall amount. The identification section uses the respective acquisition results of the detection result acquisition section and the weather information acquisition section to identify flooding of the road.