An anomaly handling method using a roadside device is disclosed. The method includes receiving, from a vehicle, an anomaly detection notification, which includes level information indicating a level affecting safety, and a location of the vehicle. The method also includes obtaining a location of the roadside device and determining whether a distance between the location of the vehicle and the location of the roadside device is within a predetermined range. When the distance is within the predetermined range and is shorter than a first predetermined distance, not changing the level information and transmitting the received anomaly detection notification externally from the one vehicle. When the distance is within the predetermined range and is longer than or equal to the first predetermined distance, changing to decrement a level indicated by the level information, and transmitting changed anomaly detection notification externally from the one vehicle.