1. A method for controlling the output of a voice guidance signal in a navigation system, the method comprising: searching for a travel route from a starting location to a destination of a vehicle; guiding the vehicle to travel along the searched travel route; determining a current vehicle location when the vehicle is traveling; searching for a target location to be guided that exists ahead of the traveling vehicle; generating a voice guidance signal for the searched target location; determining a priority according to a distance relationship between the current vehicle location and the searched target location and a specific characteristic of the searched target location; assigning the priority to the generated voice guidance signal in advance; and outputting the generated voice guidance signal in conflict with an output of a plurality of voice guidance signals when the generated voice guidance signal has a highest priority, wherein determining the priority comprises: designating a voice guidance signal for guiding arrival at a destination with a first priority; designating a last voice guidance signal issued just before the vehicle passes by a predetermined target location to be guided with a second priority when the predetermined target location to be guided is guided three times with voice guidance signals including initial, intermediate and last voice guidance signals; designating a voice guidance signal for guiding a dangerous area with a third priority; designating an initial or intermediate voice guidance signal for the predetermined target location to be guided with a fourth priority; and designating a voice guidance signal for guidance of a joining point, an entrance to a comfort stop, straight driving, or a registration area with a fifth priority.