A control circuit detects a current position of a subject vehicle on a map. Before executing a driving assistance application, the control circuit computes a map reliability degree by using a positioning accuracy coefficient, a time-based change coefficient, and an information accuracy coefficient. The positioning accuracy coefficient indicates a positioning accuracy of map data with respect to a target spot. The time-based change coefficient indicates a time-based change of the map data from the latest investigation for the target spot. The information accuracy coefficient indicates an accordance ratio of the map data relative to actual data with respect to multiple information items related to the target spot. The map data can be used for executing the driving assistance application when the product of (i) a required accuracy designated to the application and (ii) the computed map reliability degree is equal to or more than a predetermined value.