This paper describes a method of measuring the cutting force by the birefringent coatings. The experiment is carried out in two-dimensional machining on annealed aluminum workpiece. The coating is a sheet of the birefringint material that is the epoxy-rubber 100 : 100 : 8 of 1mm thickness. This method has many advantages over other methods of all kinds of tool dynamometer. It provides useful data that enable the investigator to show the complete distribution of cutting strain and to be determined of the cutting force at the same time. The residual strain by the cutting is also observed. It is found that the photo-elastic coating method is applicable not only to elastic material but also to ductile workpiece through this experiment.