Disclosed is a method of extracting ridge and valley lines from three-dimensional point data, the method including the steps of: receiving undefined point data obtained from a three-dimensional scanning system; estimating a normal vector by principal component analysis so as to calculate a normal vector with regard to each received point; and on the basis of such information, creating a moving least squares (MLS) surface of points approximation with regard to each received point. Then, Delaunay edge is created by a Voronoi diagram with regard to each point from the created MLS surface of points; and ridge (or valley) points are extracted by measuring zero-crossing on each Delaunay edge. Ridges and valleys as lines are created by connecting the extracted ridge points in a principal curvature direction. The extraction of ridge and valley lines is used as a pre-processing step for creating three-dimensional points into mesh data, and is advantageous for identifying general model features.