A route guidance method in a navigation system using a wireless network, wherein a navigation terminal receives route guidance data by which a moveable object is guided to a destination via a plurality of node points in an optimum route from an information center. The navigation terminal determines whether a user has requested a preview of an optimum route. If the preview has been requested, the navigation terminal determines whether preview information is to be provided in text or in image. Upon request for the preview in text, the navigation terminal displays comprehensive route information in text. Upon request for the preview in image, the navigation terminal generates preview information about each node point on the optimum route based on the route guidance data and displays the preview information in image.