A danger detection system for detecting a danger on a road, the danger that changes over time and may not be a danger due to the change over time, the danger detection system including a vibration acquisition unit 11 configured to acquire an acoustic signal collected by a microphone mounted on a vehicle when the vehicle passes through a region on a predetermined road, a danger determination unit 12 configured to determine whether the acoustic signal is derived from the danger, a danger location detection unit 2 configured to determine whether the danger is present in the region on the predetermined road based on the number of times an acoustic signal acquired from each of the plurality of vehicles is determined to be derived from the danger, and a danger information notification unit 3 configured to notify a communication device that can pass through the region on the predetermined road of danger information that is information about a region on a road determined to have a danger.