The establishment of test methods for determination of the tension softening diagrams of concrete has been desired. In this contribution, following the discussions on the existing J-integral approaches a simple and handy test method for determination of the tension softening diagrams from bending tests on notched beams is proposed. The method has the following features: (1) the tension softening diagrams can be determined from a single beam specimen, (2) the method can be combined with the RILEM method for determination of the fracture energy G_F, (3) only the load, the loading point displacement and the crack opening at the notch tip are necessary to be measured, (4) the second derivative of the potential energy is introduced to improve the accuracy of the estimation of the diagrams. The proposed method is applied to concretes including high strength concrete and light weight concrete to determine tension softening diagrams, and the validity of the method is certified.