A support control unit for determining a traveling condition of a host vehicle during an exit from a main road to an access road determines whether or not the condition of the host vehicle at a given point in time corresponds to an exit start scene or an exit completion scene for detecting the start of an exit or completion of the exit on the basis of a host vehicle position, route data, map rendering data, or lane information including at least road surface marking positions, and determines that an exit start timing or an exit completion timing of the host vehicle has arrived when the condition is determined to correspond to the exit start scene or the exit completion scene. Hence, during the exit from the main road to the access road, the traveling condition of the host vehicle can be determined accurately. The support control unit also determines the traveling condition of the host vehicle during convergence with the main road from the access road.