Abstract: Aspects relate to determining a priority based on impact on the surrounding environment according to the type of the event, thereby preventing the occurrence of secondary events resulting from the event and improving the efficiency and safety of event countermeasures in smart cities. Provided is a priority determination device including a sensor group for acquiring sensor information, an analysis unit for detecting, by analyzing the sensor information, occurrence of an event and determining an event feature related to the detected event, a surrounding impact determination unit for determining, for an impact region that has a possibility of being impacted by the event, a surrounding impact parameter that indicates an impact of the event on the impact region based on the event feature related to the event, and a priority calculation unit for determining a priority of the event based on at least the surrounding impact parameter.