By a statistical approach scratch method (measuring method of wheel surface topography) is analyzed theoretically and experimentally. Results are summarized as follows: (1) Grain cutting edge density obtained by scratch method is that of effective cutting edges which have effective concern with roughness generation. (2) The measuring accuracy in scratch method is improved by an increase in scratch depth and width, (3) Measuring process in scratch method is the same in essence as that of COFG (cluster overcut fly grinding) test, and there is no choice between the two. (4) Scratch method has a good point that the measuring device is simple and easy to handle, but has a difficult one that a considerably long time is expended on data processing, so an improved scratch method which can shorten the time is developed.