VEHICLE-USE REAR SIDE WARNING DEVICE AND VEHICLE-USE REAR SIDE WARNING METHOD

An approaching moving object detecting unit () that detects an approaching moving object existing within a predetermined range on a rear side of an own vehicle based on outputs of a periphery monitoring camera unit () that acquires an image of the rear side of the own vehicle and a sensor unit () that detects an approaching moving object, a relative speed detecting unit () that detects relative speeds of an approaching moving object and the own vehicle, and a warning output determining unit () that, when an approaching moving object is detected and the own vehicle is attempting to change lane, causes a warning of a warning output unit () to be generated when a relative speed detected by the relative speed detecting unit () exceeds a reference relative speed with respect to which a lane change can be carried out, are provided with an object of restricting an excessive notification when notifying of the existence of an approaching moving object.