A detection unit for detecting a data row of a press position and a load at the press position; an input/storage unit for inputting and storing a value serving as a reference for determining a bend point in a relation between the press position and the load at the press position; a data-row calculation unit for calculating a data row of a press position and a load at a constant distance interval based on the data row of the press position and the load detected; a slope calculation unit for calculating a slope of the load based on the press position and the load at the press position detected; and a bend-point determination unit for determining a point, at which the calculated slope of the load exceeds the value serving as the reference for determining the bend point, as the bend point are provided.