A data analysis apparatus , comprising: a vehicle data obtainer configured to obtain vehicle data indicating a vehicle status of a first vehicle ; an external data obtainer configured to obtain external data indicating an external circumstance of the first vehicle from at least one of a second vehicle and a traffic infrastructure system , the second vehicle being in an area where the first vehicle is running, the second vehicle being different from the first vehicle ; and a determiner configured to perform a first determination as to whether there is an inconsistency between the vehicle status of the first vehicle and the external circumstance, and outputs a result of the first determination regarding the first vehicle , the vehicle data obtainer is configured to obtain the vehicle data from each of a plurality of first vehicles each being the first vehicle , the plurality of first vehicles being in the area, and the determiner is configured to perform the first determination on the vehicle data obtained from each of the plurality of first vehicles , and output results of the first determinations, perform a second determination as to whether or not a number of one or more results each indicating that there is the inconsistency is at or higher than a predetermined reference, the one or more results being included in the results of the first determinations for the plurality of first vehicles , and output (i) a result of the second determination indicating that the external data has an anomaly when the second determination is made that the number is at or higher than the predetermined reference, and characterised in that the determiner is configured to output (ii) a result of the second determination indicating that one or more first vehicles corresponding to the one or more results each indicating that there is the inconsistency among the plurality of first vehicles have an anomaly when the second determination is made that the number is less than the predetermined reference. a vehicle data obtainer configured to obtain vehicle data indicating a vehicle status of a first vehicle ; an external data obtainer configured to obtain external data indicating an external circumstance of the first vehicle from at least one of a second vehicle and a traffic infrastructure system , the second vehicle being in an area where the first vehicle is running, the second vehicle being different from the first vehicle ; and a determiner configured to perform a first determination as to whether there is an inconsistency between the vehicle status of the first vehicle and the external circumstance, and outputs a result of the first determination regarding the first vehicle , the vehicle data obtainer is configured to obtain the vehicle data from each of a plurality of first vehicles each being the first vehicle , the plurality of first vehicles being in the area, and the determiner is configured to perform the first determination on the vehicle data obtained from each of the plurality of first vehicles , and output results of the first determinations, perform a second determination as to whether or not a number of one or more results each indicating that there is the inconsistency is at or higher than a predetermined reference, the one or more results being included in the results of the first determinations for the plurality of first vehicles , and output (i) a result of the second determination indicating that the external data has an anomaly when the second determination is made that the number is at or higher than the predetermined reference, and characterised in that the determiner is configured to output (ii) a result of the second determination indicating that one or more first vehicles corresponding to the one or more results each indicating that there is the inconsistency among the plurality of first vehicles have an anomaly when the second determination is made that the number is less than the predetermined reference. <EOS>