A vehicle travel support device capable of continuing operation even when the recognition accuracy of a lane mark has been degraded, and the like, wherein the degree of control on the operation of a steering device or the like is set higher as the reliability of a lane mark becomes higher. In a state in which the reliability of a travel area demarcated by the lane mark is high, a vehicle's travel is relatively strongly or actively supported so that the vehicle will not depart from the travel area. On the other hand, the degree of control on the operation of the steering device or the like is set lower as the reliability of the lane mark is lower. In a state in which the reliability of the travel area demarcated by the lane mark is low, the vehicle's travel is relatively weakly or passively supported so that the vehicle will not depart from the travel area.