A navigation device which acquires differential map data in a differential map data set from a map delivery server via a communication line and updates map data, comprising: a setting section that sets a destination of a vehicle; a display unit that displays a navigation route from a current position of the navigation device to the destination; a map database that stores therein map data for computing the navigation route; a differential map data storage unit that stores therein the differential map data acquired from the map delivery server; a memory unit that memorizes cache map data which is map data on a surrounding area of the navigation device; a satellite radiowave receiving unit that receives information on the current position of the navigation device using radiowave from a satellite; an intersection candidate information acquisition section that transmits intersection candidate request information including the current position, the destination, and version information on the map data held by the navigation device to the map delivery server and acquires intersection candidate information which is information on one or more candidates of a new intersection on the navigation route from the map delivery server; and a differential map data acquisition section that acquires the differential map data in the differential map data set, the data including the intersection, from the map delivery server, and stores the acquired data in the differential map data storage unit; characterized in that it further comprises an update map data selection section that compares an arrival time from the current position of the navigation device to each of the candidates of an intersection with a time required for updating the data stored in the differential map data storage unit and selects data in the differential map data set updatable in time before the vehicle arrives at the respective intersection, from among all data in the differential map data set stored in the differential map data storage unit; an update order determination section that determines an order of updating data in the differential map data set selected by the update map data selection section such that the data in the update map data set is arranged in order of arrival times at the candidates of intersection from shortest to longest; and a map data update processing section that updates the map database for the data in the differential map data set selected by the update map data selection section according to the update order determined by the update order determination section and also updates the cache map data stored in the memory unit using the data in the updated map database. a setting section that sets a destination of a vehicle; a display unit that displays a navigation route from a current position of the navigation device to the destination; a map database that stores therein map data for computing the navigation route; a differential map data storage unit that stores therein the differential map data acquired from the map delivery server; a memory unit that memorizes cache map data which is map data on a surrounding area of the navigation device; a satellite radiowave receiving unit that receives information on the current position of the navigation device using radiowave from a satellite; an intersection candidate information acquisition section that transmits intersection candidate request information including the current position, the destination, and version information on the map data held by the navigation device to the map delivery server and acquires intersection candidate information which is information on one or more candidates of a new intersection on the navigation route from the map delivery server; and a differential map data acquisition section that acquires the differential map data in the differential map data set, the data including the intersection, from the map delivery server, and stores the acquired data in the differential map data storage unit; an update map data selection section that compares an arrival time from the current position of the navigation device to each of the candidates of an intersection with a time required for updating the data stored in the differential map data storage unit and selects data in the differential map data set updatable in time before the vehicle arrives at the respective intersection, from among all data in the differential map data set stored in the differential map data storage unit; an update order determination section that determines an order of updating data in the differential map data set selected by the update map data selection section such that the data in the update map data set is arranged in order of arrival times at the candidates of intersection from shortest to longest; and a map data update processing section that updates the map database for the data in the differential map data set selected by the update map data selection section according to the update order determined by the update order determination section and also updates the cache map data stored in the memory unit using the data in the updated map database.