Transmission necessity determination apparatus and route planning system

A transmission necessity determination apparatus configured to determine whether or not to transmit road-related data acquired by a vehicle-mounted system to a server from a vehicle includes: a stability acquisition unit configured to acquire a stability of the vehicle-mounted system for each position from the vehicle-mounted system; and a transmission necessity determination unit configured to determine whether or not to transmit the road-related data to the server from the vehicle based on at least one of the collection degree of the road-related data for each position on the map and the freshness of the road-related data for each position and the stability of the vehicle-mounted system for each position.