1. A system for drawing a stream and road centerline based on a Geographic Information System (GIS), the system comprising: a system main module configured to drive the system for drawing the stream and road centerline necessary for accurate GIS-based linear map production; a spatial database in which a graphic database for storing a plurality of pieces of graphic data, in which positional information of points of a stream and road contour line is stored in the form of a digital map, is established; a centerline vertex position automatic detecting and storing module included in the system main module and configured to perform a preprocessing process of retrieving data of a region where centerline drawing is necessary, to automatically detect the positions of points, through which the centerline passes, and potential vertexes which will be included in the centerline in the future, and to extract and store the positional information of the points in the form of a digital map; a centerline drawing, editing and storing module included in the system main module and configured to draw and edit the centerline using the positional information of the vertexes processed by the centerline vertex position automatic detecting and storing module and to store the centerline as a linear map; and a display unit configured to display the result of drawing the centerline using the system on a screen, wherein the centerline vertex position automatic detecting and storing module performs the preprocessing procedure of retrieving a stream or road map stored in the spatial database and transforming the stream or road map into data available in the module, includes an algorithm for detecting a maximum inscribed circle of the points which are the positions of the potential vertexes of the centerline, and a center point of the maximum inscribed circle, transforms the extracted positional information of the potential vertexes into a digital map, and stores the digital map, and wherein the centerline drawing, editing and storing module retrieves the vertexes extracted and stored by the centerline vertex position automatic detecting and storing module, performs snapping configuration for detecting the accurate positions of the vertexes based on the GIS and configuration for generating a new linear graphic, confirms and selects the positions of the vertexes extracted in a GIS-based environment, linearly connects and edits the vertexes, and stores the final result of connecting the centerlines as a linear digital map file.