The deformation of plastic bending in the sheet metal working is so complex that the analysis is very difficult. The purpose of our research is to get the hint of solution of this problem. So we compared the results of the calculation with that of the bending tests which performed with aluminium plate 1.5 mm in thickness. At first, we performed tension tests to determine tensile stress-strain diagram, and compressive stress-strain diagram was determined from the results of bending tests. Next, we obtained the relation between bending moment M and bending angle θ in these cases where the neutral axis does not change, the neutral axis changes and the breadth is very wide. Then, we compared these results with the bending moment M and the bending angle θ which we got by the experiment. The conclusion is that the analysis of bending may be based on the results of the tension tests only.