A vehicle-mounted apparatus includes a communication unit configured to receive data from an outside, a generation unit configured to generate from the data, dynamic maps in each of which dynamic information regarding a dynamic object is associated with a static map, a storage unit configured to store the dynamic maps and the static map, and a determination unit configured to determine whether to update a dynamic map, among the dynamic maps stored in the storage unit, corresponding to a specific region of the static map. The determination unit determines, in accordance with a degree of certainty of the dynamic map corresponding to the specific region, whether to update the dynamic map, and in response to the determination unit determining that the dynamic map is to be updated, the generation unit updates the dynamic map with a new dynamic map generated from data newly received by the communication unit.