A warning device (1; 1A; 1B) comprising: a driver biological information acquisition unit configured to acquire biological information on a driver; a driver arousal level estimation unit configured to estimate an arousal level of the driver on the basis of the biological information; a vehicle behavior information acquisition unit configured to acquire behavior information indicating a behavior of a vehicle; and a warning unit (30; 30A; 30B) configured to issue a warning based on arousal level information indicating the arousal level and the behavior information, wherein the vehicle behavior information acquisition unit further includes a driving support warning generation unit configured to generate driving support warning information for causing a driving support warning to occur on the basis of the behavior information, the warning device (1; 1A; 1B) further comprises a driving tendency analysis unit configured to manage, as history information, a history of a driving support warning with respect to the behavior information in association with the arousal level of the driver, on the basis of the arousal level information and the driving support warning information, and analyze a driving tendency of the driver on the basis of the history information to acquire analysis information, and the warning unit (30; 30A; 30B) issues a warning corresponding to the driving tendency on the basis of the analysis information. a driver biological information acquisition unit configured to acquire biological information on a driver; a driver arousal level estimation unit configured to estimate an arousal level of the driver on the basis of the biological information; a vehicle behavior information acquisition unit configured to acquire behavior information indicating a behavior of a vehicle; and a warning unit (30; 30A; 30B) configured to issue a warning based on arousal level information indicating the arousal level and the behavior information, wherein the vehicle behavior information acquisition unit further includes a driving support warning generation unit configured to generate driving support warning information for causing a driving support warning to occur on the basis of the behavior information, the warning device (1; 1A; 1B) further comprises a driving tendency analysis unit configured to manage, as history information, a history of a driving support warning with respect to the behavior information in association with the arousal level of the driver, on the basis of the arousal level information and the driving support warning information, and analyze a driving tendency of the driver on the basis of the history information to acquire analysis information, and manage, as history information, a history of a driving support warning with respect to the behavior information in association with the arousal level of the driver, on the basis of the arousal level information and the driving support warning information, and analyze a driving tendency of the driver on the basis of the history information to acquire analysis information, and the warning unit (30; 30A; 30B) issues a warning corresponding to the driving tendency on the basis of the analysis information.