In-vehicle device and map updating system

An in-vehicle device includes: a storage unit storing map information divided into zones and used at least for screen display; a map drawing unit generating screen information using the map information; a difference detecting unit calculating, as a difference evaluation value, a magnitude of a difference in zone between the map information before update and the map information after update; and a map updating unit determining an order of updating the zones on a basis of a magnitude of the difference evaluation value to update, for each of the zones, the map information stored in the storage unit.