A GNSS device control method for controlling a global navigation satellite system (GNSS) device installed in a movement means, the method comprising by a GNSS device control system, acquiring map data; by the GNSS device control system, periodically performing a predetermined first process while the GNSS device is active; and by the GNSS device control system, periodically performing a predetermined second process while the GNSS device is deactivated, wherein the first process includes: acquiring position information and movement direction information of the movement means from the activated GNSS device; attempting (S110, S120) to determine a road on which the movement means is traveling based on the map data and the position information and movement direction information of the movement means; and deactivating the activated GNSS device when a travel road on which the movement means is in travel is determined, and wherein the second process includes: acquiring measured data from an inertial measurement unit; acquiring speed data from a speed sensor; calculating a predicted position and a predicted movement direction of the movement means based on the measured data and the speed data; determining (S220, S230) whether or not the movement means deviates from the travel road based on the map data and the predicted position and the predicted movement direction of the movement means; and activating the deactivated GNSS device when determined to deviate by a GNSS device control system, acquiring map data; by the GNSS device control system, periodically performing a predetermined first process while the GNSS device is active; and by the GNSS device control system, periodically performing a predetermined second process while the GNSS device is deactivated, wherein the first process includes: acquiring position information and movement direction information of the movement means from the activated GNSS device; attempting (S110, S120) to determine a road on which the movement means is traveling based on the map data and the position information and movement direction information of the movement means; and deactivating the activated GNSS device when a travel road on which the movement means is in travel is determined, and acquiring position information and movement direction information of the movement means from the activated GNSS device; attempting (S110, S120) to determine a road on which the movement means is traveling based on the map data and the position information and movement direction information of the movement means; and deactivating the activated GNSS device when a travel road on which the movement means is in travel is determined, and wherein the second process includes: acquiring measured data from an inertial measurement unit; acquiring speed data from a speed sensor; calculating a predicted position and a predicted movement direction of the movement means based on the measured data and the speed data; determining (S220, S230) whether or not the movement means deviates from the travel road based on the map data and the predicted position and the predicted movement direction of the movement means; and activating the deactivated GNSS device when determined to deviate acquiring measured data from an inertial measurement unit; acquiring speed data from a speed sensor; calculating a predicted position and a predicted movement direction of the movement means based on the measured data and the speed data; determining (S220, S230) whether or not the movement means deviates from the travel road based on the map data and the predicted position and the predicted movement direction of the movement means; and activating the deactivated GNSS device when determined to deviate